During the meeting, Mr Cameron invited leaders of the Council to establish a formal office in London, as fighting in Libya continued.
Mr Cameron said the UK presence in Benghazi would also be boosted.
The PM said:
These steps continue our very clear intention to work with the council to ensure Libya has a safe and stable future, free from the tyranny of the Gaddafi regime.
Mr Cameron said the two leaders discussed events in Libya and how to build the future that the Libyan people deserved.
I have been struck again today by their bravery in standing up to a tyrant who is still today killing innocent people.
It is impossible to imagine a real future for Libya with Gaddafi in power,” he said, adding: “The council represents the future of Libya as much as Gaddafi represents its past.
Mr Jalil said he had come to London to express his gratitude to the British people and their Government “for their discipline and moral stand” in supporting the rebellion.
This stand was not based on any benefit that the British Government may derive from this support. It is a humanitarian position. I assure you that you will never regret taking this stand.
We appreciate what the Prime Minister has said, in terms of increasing military support through Nato, in terms of providing protection for civilians, and about economic help in accordance with the law, because we are a people of law and we respect the law.
Earlier today Mr Jalil also met Deputy Prime Minister Nick Clegg and will later hold talks with Foreign Secretary William Hague.