Correspondence

Non-human primates bred for use in scientific purposes: response from Lord Hanson (accessible)

Published 15 September 2025

Lord Hanson of Flint
Minister of State
2 Marsham Street
London
SW1P 4 DF

Dr Sally Robinson
Chair of the Animals in Science Committee (ASC)
By email only

13 August 2025

Dear Dr Robinson,

Thank you for the Committee’s report of 23 June 2022 regarding the Home Office’s commission to the Animals in Science Committee (ASC) for advice on implementing restrictions on the use of non-human primates (NHPs) in scientific procedures.

I appreciate the Committee’s detailed work and clear recommendations. The Home Office accepts all the ASC’s recommendations (Annex A) and will implement them through the attached policy (Annex B). It is our aspiration that the vast majority of NHPs used for scientific purposes in Great Britain come from self-sustaining colonies and are second generation bred in captivity. The phased approach we will take will allow the science sector sufficient time to adapt and commits to the prioritisation of welfare and ethical standards.

I would like to acknowledge the delay in responding, which was due to several factors. Stakeholder engagement began in 2023 to gather feedback on the recommendations and proposed policy. While stakeholders were already moving towards this policy position, they needed time to adjust supply-side activities to begin meeting the new requirements. In addition, work in 2023/24 on statistics collection highlighted a lack of clarity around the number of self-sustaining colonies. Further data had to be prepared to support the policy and inform the new guidance.

I am also grateful to the Committee for its recommendation on the development of an alternatives strategy. As I communicated to you earlier this month, the government will soon publish an alternatives strategy to accelerate the development and validation of alternative methods. This will be our vehicle for delivering the manifesto commitment to work towards a vision of phasing out the use of animals in science, alongside Lord Vallance, Baroness Hayman, and myself. I will keep you updated.

Thank you again for your valuable input.

Yours sincerely,

Rt Hon. Lord Hanson of Flint
Minister of State

Annex A: Animals in Science Committee Recommendations and Actions Taken

Recommendation 1

A universal definition of F0, F1, F2 and ‘self-sustaining colony’ should be used across all guidance, reports, and communications.

Home Office response

Accepted.

Actions taken

The Home Office has set out clear definitions, which will be incorporated in future publications (data will be collected from 2026 and reported in 2027).

Recommendation 2

The definitions of NHP generation, and self-sustaining colony used, for NHPs in the annual animal use statistics for 2020 and 2021 should be clarified. The data in published reports should be amended where needed to ensure that the data is accurate for readers, and so that any future benchmarking comparisons made on this issue are accurate, informative and can take account of the differing definitions that have been used over time.

Home Office response

Accepted.

Actions taken

On 17 November 2022, the Home Office updated the definitions of non-human primates generation and colony status in the annual animal use statistics for 2020 and 2021. This followed correspondence to the ASC of 14 November 2022. – No further action required.

Recommendation 3

There should be a single definition for ‘self-sustaining colony’ across all NHP species.

Home Office response

Accepted.

Actions taken

The Home Office has set out a clear definition for all NHP species, with the exception of marmosets for which the existing definition set out in the Animals (Scientific Procedures) Act 1986 will continue to apply. Should there be an opportunity to amend the legislation in the future, the Home Office will consider implementing a single universal definition.

Recommendation 4

The definition of ‘self-sustaining colony’ must incorporate the concept of the colony being ‘permanently closed’ to further introductions of male or female animals (unless they originate from other existing ‘closed’ colonies) and should also preclude the addition of any individuals newly captured from the wild after a fixed date.

Home Office response

Accepted.

Actions taken

Home Office has incorporated this in the definition for self-sustaining colony. No wild-caught animals can be added to self-sustaining colonies after 01 August 2025 (with the exception of marmosets where the definition of self-sustaining colony in ASPA Schedule 2C Section 25(d) will continue to apply).

Recommendation 5

All UK-based establishments breeding NHPs for use in the UK should meet the UK definition of a ‘self-sustaining’ colony from November 2022 onwards.

Home Office response

Accepted.

Actions taken

The Home Office can confirm that all establishments breeding NHPs in Great Britain meet the definition of self-sustaining colony.

Recommendation 6

The date used as the starting point for classifying overseas breeders as self-sustaining should be established to act as the greatest encouragement for breeders, who have not already done so, to move to being ‘self-sustaining’ in policy and practice. For the animals supplied to the UK we suggest this permanently fixed date could be set at November 2022.

Home Office response

Accepted.

Actions taken

The Home Office definition of self-sustaining colony is designed to encourage the formation of self-sustaining colonies. After the fixed date 01 August 2025, no wild-caught NHPs may be added to a self-sustaining colony.

Recommendation 7

Until the goal of sourcing NHPs only from self-sustaining colonies can be achieved for all species of NHPs, we recommend that UK policy should be that, as from November 2022, all NHPs used must be either:

• F2/F2+ (i.e. offspring where both parents have been bred in captivity)
• from a self-sustaining colony

Under this policy, the use of F1 NHPs would be acceptable only if coming from a (closed) self-sustaining colony.

Home Office response

Accepted.

Actions taken

With effect from 1 July 2025, the Home Office will only grant new licence authority for the use of NHPs from self-sustaining colonies and/or those bred as second-generation (F2) in captivity.

For Cynomolgus macaques, a time-limited transitional period will apply from the start of the policy (1st August 2025) to 1st August 2026. During this period, the use of first-generation (F1) Cynomolgus macaques not from self-sustaining colonies will be permitted when the establishment applying for a licence can demonstrate where:

a) There is a scientific need,

b) The inability to reasonably source F2/F2+ or self-sustaining Cynomolgus macaques, and a robust plan (see below), to transition to a sustainable supply of F2/F2+ or self-sustaining NHPs

c) The use of Cynomolgus macaques will prevent culling, thereby reducing harm.

The policy will be reviewed from 1st April 2026 by the Animals in Science Regulation Policy Unit and will involve consultation with the ASC and industry stakeholders. A decision will subsequently be made on whether to end or extend the transitional period.

Recommendation 8

Any requests to use F1 NHPs not from a self-sustaining colony (i.e. where individuals are still taken from the wild to replenish breeding stock) should require special justification on a case-by-case basis, and before animals are imported. In any case, this should only be allowed until November 2024 (for more on this, see later section answering Commissioned Question 4). As this measure would likely require co-ordination and input from different UK Government departments, the ASC is happy to work with the Home Office to develop a system for how this could work in practice.

Home Office response

Accepted.

Actions taken

Any application to use F0 or F1 NHPs not from a self-sustaining colony (with the exception of Cynomolgus macaques during the time-limited transitional period – see recommendation 7) will require scientific justification and be referred to the ASC for advice.

To retain genetic diversity in colonies, the Regulator will consider applications for introducing NHPs not from self-sustaining colonies. Applications for this purpose will be submitted to the ASC for advice before the Regulator approves applications. The Home Office will monitor this issue and review the policy if necessary.

The Home Office does not intend to implement an additional process requiring special justification before NHPs are imported, as the current requirements are proportionate given the availability of Cynomolgus macaques from Self-sustaining colonies.

Recommendation 9

Subject to ASPA Schedule 2C 25(3), the use of F0 NHPs in scientific procedures within the UK should continue to be prohibited.

Home Office response

Accepted.

Actions taken

No action required.

Recommendation 10

Requirements for NHPs only to be used in research and testing in the UK where they are the offspring of NHPs bred in captivity, or where they come from a ‘self-sustaining colony’ should apply to all species of NHPs.

Home Office response

Accepted.

Actions taken

The Home Office will introduce restrictions on 1st August 2025. Subject to the exemptions for scientific justification and a time-limited transition for Cynomolgus macaques from 1st August 2025 to 1 August 2026.

Recommendation 11

The requirement for all NHPs used in scientific procedures in the UK to be F2/F2+, or to come from self-sustaining colonies, should take effect from November 2022.

Home Office response

Accepted.

Actions taken

The Home Office will introduce restrictions on 1st August 2025 on all non-human primates (NHPs) except Cynomolgus macaques, where a time-limited transition period applies due to global supply issues. However, establishments needing exceptions will be encouraged to meet this requirement as soon as possible.

Recommendation 12

Given the impact the current decision by China to stop exporting macaques has had on the global supply of NHPs, in combination with other factors, we recognise that in the case of cynomolgus macaques only, there is an argument for implementing a time-limited exemption period to the UK requirement for all NHPs used to be either F2/F2+ or sourced only from self-sustaining colonies. We suggest an appropriate period would be for two years - until November 2024. This will enable users of imported cynomolgus macaques in the UK to stabilise alternative supplies (as well as providing additional time for China to lift its export ban as the world continues to come out of the worst aspects of the pandemic). N.B. as per our Recommendation 7, the use of F1 NHPs would still be permitted where these animals come from genuinely ‘self-sustaining’ colonies.

Home Office response

Accepted.

Actions taken

The use of first-generation (F1) Cynomolgus macaques not from self-sustaining colonies will be permitted when the establishment applying for a licence can demonstrate where:

a) There is a scientific need,

b) The inability to reasonably source F2/F2+ or self-sustaining Cynomolgus macaques, and a robust plan (see below), to transition to a sustainable supply of F2/F2+ or self-sustaining NHPs

c)The use of Cynomolgus macaques will prevent culling, thereby reducing harm.

The transitional period for Cynomolgus macaques will be from the start of the policy (1st August 2025) to 1st August 2026. The policy will be reviewed from 1st April 2026 by the Animals in Science Regulation Policy Unit and will involve consultation with the ASC and industry stakeholders. A decision will subsequently be made on whether to end or extend the transitional period.

Recommendation 13

During this time, we recommend that the UK government, as well as organisations supplying, and establishments using, imported cynomolgus macaques in scientific procedures should directly liaise with overseas breeding centres (e.g. in Mauritius and elsewhere) to strongly encourage them (or at least in the first instance the part of their operation which supplies NHPs to the UK) to put in place the policies and measures that would enable them to be truly and permanently ‘self-sustaining’ going forwards.

Home Office response

Accepted.

Actions taken

The introduction of the time-limited transitional period will allow time regulated establishments in Great Britain to engage with overseas suppliers to meet the new policy requiring the use of Closed Self-sustaining colonies.

Recommendation 14

As is also contained within the Directive, there should be a general provision to allow an exemption to the requirement to only use F2/F2+, or individuals from self-sustaining colonies, where there is legitimate and compelling ‘scientific justification’. Should any application be received by the Government regulator (e.g., the Animals in Science Regulation Unit) which seeks to invoke this exemption, then these should be passed to the Animals in Science Committee to review and provide advice on, on a case-by-case basis.

Home Office response

Accepted.

Actions taken

Any application to use F0 or F1 NHPs not from a self-sustaining colony (with the exception of Cynomolgus macaques during the time-limited transitional period) will require scientific justification and be referred to the ASC for advice.

Recommendation 15

The UK Government could consider taking steps that would enable the UK to be more self-sufficient in the supply of cynomolgus macaques, in a similar way as has been established for the use of rhesus macaques and for common marmosets in academia, and for cynomolgus macaque use by government agencies.

Home Office response

Accepted.

Actions taken

The regulator will require that all relevant scientific establishments have NHP sustainability plans in place to transition to only using NHPs from self-sustaining colonies and/or second-generation bred in captivity NHP sustainability plans must include, at a minimum:

a. A robust plan and timeframe to transition (if not already undertaken);

b. Specific actions being taken to deliver the transition (if not already undertaken); and,

c. An effective due diligence process to ensure NHPs used are classified accurately (if not already undertaken)

Recommendation 16

The UK Government should continue to engage in, and accelerate and expand where possible, efforts to reduce the demand for the use of cynomolgus macaques - primarily in regulatory testing - via working collaboratively with key stakeholders.

Home Office response

Accepted.

Actions taken

The government aims to reduce the use of animals in science, including NHPs, and is actively engaging with key stakeholders to explore several initiatives. These will be announced subject to ministerial clearance.

Annex B: Policy: Improving the welfare of non-human primates bred for use in scientific research

1. Strengthen NHP definitions and improve data

The Home Office will adopt strengthened and consistent definitions of NHPs and self-sustaining colony status.

Generational status will be defined as follows:

• F0: wild-caught primates.
• F1: first generation of primates bred in captivity, where either the mother or father is F0.
• F2: second generation of primates bred in captivity, offspring of primates bred in captivity, where both the mother or father are F1 or higher.

Self-sustaining colonies will be defined as follows (except for marmosets):

a) The colony is kept in captivity in a way that ensures the animals are accustomed to humans;

b) The colony consists only of animals that have been bred in captivity, or no F0 animals have been added to the colony after 1 August 2025; and,

c) The colony is sustained only by animals being bred within the colony or animals being sourced from other colonies that meet the requirements in (a) and (b).

Changes to the current definitions are as follows:

1. NHPs will only be classed as second-generation bred in captivity (F2) when both parents are bred in captivity (F1 or higher) (any NHP with a wild-caught (F0) parent will not be considered as F2).

2. No wild-caught animals can be added to self-sustaining colonies after 1 August 2025 (with the exception of marmosets where the definition of self-sustaining colony in ASPA Schedule 2C Section 25(d) will continue to apply).

To retain genetic diversity in colonies, the Regulator will consider applications for introducing NHPs not from self-sustaining colonies. Applications for this purpose will be submitted to the ASC for advice before the Regulator approves applications. The Home Office will monitor this issue and review the policy if necessary.

The Home Office will publish data against the definitions above in the annual statistics from 2027 to track progress, provide transparency, and inform future policy.^{[footnote 1]}

2. Introduce restrictions

With effect from 1 August 2025, new licence authorisations will only be granted for the use of NHPs from self-sustaining colonies and/or those bred as second-generation (F2) in captivity, as defined above.

A permanent general exemption will apply where there is scientific justification. This is consistent with the use of F0 NHPs, which remain prohibited except where there is scientific justification (ASPA Schedule 2C 25(3)). Any application to use F0 or F1 not from a self-sustaining colony will be referred to the ASC for advice.

3. Introduction of a temporary transitional exception period for Cynomolgus Macaques

The purpose of the time-limited transition period is to give the industry time to adjust to meet the new requirements.

During this period, the use of first-generation (F1) Cynomolgus macaques not from self-sustaining colonies will be permitted when the establishment applying for a licence can demonstrate where:

a) There is a scientific need,

b) The inability to reasonably source F2/F2+ or self-sustaining Cynomolgus macaques, and a robust plan (see below), to transition to a sustainable supply of F2/F2+ or self-sustaining NHPs

c) The use of Cynomolgus macaques will prevent culling, thereby reducing harm.

The transitional period for Cynomolgus macaques will be from the start of the policy 1st August 2025 to 1st August 2026. The policy will be reviewed from 1st April 2026 by the Animals in Science Regulation Policy Unit and will involve consultation with the ASC and industry stakeholders. A decision will subsequently be made on whether to end or extend the transitional period.

4. Sustainability plans for sourcing NHPs.

The Home Office will require that all relevant scientific establishments have NHP sustainability plans in place to transition to only using NHPs from self-sustaining colonies and/or second-generation bred in captivity. Relevant scientific establishments are those that use or intend to use NHPs in scientific procedures that are not from self-sustaining colonies and/or second-generation bred in captivity.

The Animals in Science Regulator will require either an NHPs sustainability plans for audit from the end of 2025, or a declaration of due diligence in process. The sustainability plan will be required from establishments making a transition to the new arrangements, the declaration will be for those establishments that already comply with the new arrangements.

NHP sustainability plans must include, at a minimum:

a) A robust plan and timeframe to transition (if not already undertaken);

b) Specific actions being taken to deliver the transition (if not already undertaken); and,

c) An effective due diligence process to ensure NHPs used are classified accurately (if not already undertaken)

Establishments sourcing NHPs from colonies that already comply with the above requirements should declare this during the audit process. They should be required to provide an effective due diligence process to ensure NHPs used are classified accurately.

1. These data classification changes may lead to an increase in the reported use of F1 animals. ↩