Martin Mubanga, 32, one of four Britons released from the American detention centre in Cuba last month, claims that an MI6 agent played an important role in having him sent there.
Mr Mubanga also claims that the agent asked him, while he was under arrest in Zambia, to spy on Islamic groups in South Africa and Leeds. "They wanted me to go where no one would know me. I suppose so I could be undercover. I refused," he said in his first newspaper interview, with The Observer.
Three weeks after he declined to co-operate, he was sent to Guantanamo Bay. Despite persistent doubts over his links to Islamic terror groups, he says that he was chained up, soaked in his own urine, subjected to conditions of extreme cold and heat, and physically abused by guards.
Charles Clarke, the Home Secretary, said yesterday that he was not organising a "specific investigation" into Mr Mubanga's claims.
He told BBC1's Breakfast with Frost: "I am absolutely unapologetic in saying it, that anybody in my job has to have national security at the centre of their concerns. And if there are people who threaten national security, it is necessary to deal with that and address it in a rigorous way.
"Media discussion about the precise conditions that arose, either in people going to Guantanamo Bay or not, are not really particularly well informed. I'm all in favour of human rights, but I'm even more in favour of our national security being protected."
The latest revelations come as Mr Clarke's methods of dealing with terror suspects will go under the spotlight again. Lawyers for the Home Secretary will try today to convince a panel of judges at a secret court hearing to return a wheelchair-bound Algerian detainee, known as G, to Belmarsh jail for allegedly breaching his bail conditions. G was freed last year from Belmarsh on bail after he had a mental breakdown.
Mr Mubanga, a former motorcycle courier who says he hopes to start a career as a rap singer using his jail experiences, described how he went to Afghanistan to study Islam soon after 11 September. After the US invasion, he fled to Pakistan where he lost his passport and a document described as his will. From there he went to Zambia, travelling on new documents sent to him by his family. But, while making a trip to visit his aunt, he was arrested by the Zambian security service and held in a series of guarded hotel rooms. In one of these he was visited by an unnamed, female American defence official and a British MI6 man who called himself Martin.
"Agent Martin", who claimed unconvincingly to be an Arsenal football fan, produced Mr Mubanga's "lost" passport and will. He claimed they had been found in a cave in Afghanistan with a list of Jewish organisations in New York.
The officials also produced a second document, a hand-written "military instruction manual". Mr Mubanga, who grew up in Kingsbury, north-west London, denied he was involved with al-Qa'ida. He insisted the handwriting on the manual was not his and denied visiting a cave in Afghanistan. Mr Mubanga believes his passport and will were somehow acquired by a Taliban fighter in Afghanistan months before his arrest - a fact that he believes was known to British and US security services.
Mr Mubanga's lawyer, Louise Christian, said she plans to launch lawsuits - against the British and Zambian governments - claiming her client's arrest, detention and transfer to Cuba breached national and international laws. Even though he was immediately arrested on his return to Britain on 23 January and questioned by anti-terrorist police officers, he was released without charge.
During the 33 months he was held, Mr Mubanga says he was humiliated by his guards. On 15 June last year, he says he was taken for routine interrogation but denied access to a toilet. His interrogator told him to go in the corner of the room. Taking a mop, the official "started covering me with my own waste, like he was using a big paintbrush, working methodically, beginning with my feet and working his way up my legs," he said.
A month before his release he says he was taken to Camp X-Ray, the higher- security part of Guantanamo. While there, he was placed under constant surveillance and denied all contact with his fellow prisoners.
Mr Mubanga said he is struggling to come to terms with his freedom, although he has been working on material for an album, Detainee, to be released under the stage name 10,007 - his Guantanamo prisoner number.
His attempts to restart a teenage romance with a woman called Angie have failed. "For three years, I was locked in a room where I couldn't walk as far as this chair that I'm sitting in to that window, and now suddenly I'm back in London. It's hard to adjust: all my friends have got engaged. Their lives have moved on," he said.Reuse content