The details of some of Colonel Muammar Gaddafi's opponents who had fled to Britain were given to Libyan spies by MI5, it has been reported.
Documents uncovered from archives in Libya reveal that agents for the British Secret Service supplied the confidential information to Gaddafi's intelligence officers, according to The Mail on Sunday.
It is claimed that in 2006 two Libyan agents were greeted at Heathrow Airport and given a safehouse in Knightsbridge and secure mobile phones.
It was revealed on Wednesday that Libyan military commander Abdel Hakim Belhadj is taking legal action against Jack Straw following allegations the former foreign secretary personally permitted his illegal rendition.
His lawyers confirmed legal papers had been served on the Labour MP after reports suggested he had signed documents that allowed the rebel to be sent back to his homeland in 2004.
Mr Belhadj, 45, claims he had been living in exile in Beijing, China, before being detained with his wife Fatima while en route to the UK where they were trying to seek asylum.
Conservative MP David Davies said the revelations unearthed from the archives suggest that MI5 was involved in "peculiar" activities towards Libyans in the UK. He said: "The operation which led to Mr Belhadj and others being extradited to Libya by the Americans was not the only operation we carried out in conjunction with the Libya security services.
"This is two years later. It involves people who have come to Britain, presumably cleared to live in Britain, being put under pressure to deal with the security service, which seems rather peculiar if this is realpolitik rather than protecting the security of the country."
Margaret Beckett, who was foreign secretary at the time, said the level of co-operation between Libyan and the UK described in the files "didn't ring any bells with me". She said it sounded like an "operational issue" and added: "If it's MI5 it's nothing to do with the Foreign Office."
The documents, classified UK/Libya Secret, are reported to reveal that Libya was told their targets could be threatened with deportation if they failed to co-operate.