Tony Blair says he has no memory of an alleged 2004 rendition case involving an ex-terror suspect who claims he was tortured after being flown to Libya.
The former prime minister said Britain had always opposed rendition and "absolutely adhered to that position".
Abdel Hakim Belhaj claims his flight from Bangkok to Libya refuelled at the UK territory of Diego Garcia, which was complicit in his illegal rendition.
He is suing the UK, MI6 and the UK commission in charge of Diego Garcia.
The legal action came after several documents emerged during the collapse of Col Muammar Gaddafi's regime last year.
Mr Blair told BBC Radio 4's The World At One programme: "About the Belhaj case, I don't have any recollection of it at all.
"There are many, many complicated reasons why the West's relationship is difficult with the Middle East but I think [rendition] is probably the least of them.
"Rendition has been the policy of successive US administrations. It remains the policy of this US administration.
"We have always had our own position. [Then Foreign Secretary] Jack Straw made it very clear at the time and as far as I know, we absolutely adhered to that position."
Mr Blair, the prime minister from 1997 to 2007, said the security services did an "important, dangerous job" and generally deserved the full support of the country.
He also said co-operation with the former Libyan regime had been important in the fight against terrorism.
Mr Belhaj believes he was rendered from Bangkok to Libya by the CIA, and claims that during his more than four years in a Libyan prison he was interrogated by agents from countries including Britain and United States.
He has since worked with Nato as one of the leaders of the forces that helped overthrow Col Gaddafi and is now a senior military commander in the new Libya.
Mr Belhaj's lawyers filed legal papers on 5 April against the Commission for the British Indian Ocean Territory - of which the island of Diego Garcia is a part.
Diego Garcia, in the Chagos archipelago, has been a military base since the island was leased to the US in the 1970s.