From 2010-2015, Leslie was been the Deputy General Secretary of Prospect - a union of 115,000 specialists, professionals and managers across the private and public sector. He was the lead negotiator for Prospect’s 34,000 civil service members with direct involvement in negotiating pay awards and pay systems, pensions and performance management schemes. The majority of his career prior to this was spent in Connect (formerly the Society of Telecom Executives), initially as the National Organiser and Director of Organisation and Development followed by eight years as the Deputy General Secretary. He was also the President of the TUC from September 2014 to September 2015, having previously been a general council member, since 2002.
The Member of the Prison Service Pay Review Body is to provide independent advice on the remuneration of governing governors and operational managers, prison officers and support grades in the England and Wales Prison Service.