A Guantanamo Bay inmate is demanding that ministers release documents that could free him from the US internment camp.

Binyam Mohamed, 30, claims in High Court documents that British agencies hold material that would show he was tortured while in custody and subjected to extraordinary rendition. His lawyers argue that if he can prove he was tortured they might be able to force the United States authorities to abandon plans to put him on trial before a military commission at Guantanamo Bay.

Mr Mohamed was born in Ethiopia and came to Britain as a teenage asylum-seeker in 1994.

He spent seven years living in the north Kensington area of London, during which he was granted leave to remain in Britain while his asylum claim was processed. Mr Mohamed attended a mosque frequented by radical Muslims who are said to have converted him to their brand of Islam and persuaded him to travel to Afghanistan in 2000. He is alleged to have taken part in fighting in Afghanistan in 2001 and was detained in Pakistan in 2002 while attempting to board a flight to Britain.

MI5 has confirmed to the parliamentary Intelligence and Security Committee (ISC) that one of its officers interviewed Mr Mohamed for three hours while he was in detention in Karachi. The detainee claims that the agent told him he was going to be rendered to an Arab country where he would be tortured. Shortly afterwards he was flown on a private Gulfstream jet to Rabat, Morocco, where Mr Mohamed claims he was subjected to 18 months of torture.

In graphic accounts given to his lawyers, Mr Mohamed claims that his torturers hung him from the walls and ceilings, beat him and repeatedly slashed his penis with a scalpel. He said: “I was in agony, crying, trying desperately to suppress myself, but I was screaming. They must have done this 20 or 30 times in maybe two hours. There was blood all over.

“They said, if you say this story as we read it, you will just go to court as a witness and all this torture will stop. I could not take it any more . . . and I eventually repeated what they read out to me. They told me to say I was with [Osama] bin Laden five or six times. Of course that was false. They continued with two or three interrogations a month. They weren't really interrogations - more like trainings, training me what to say.”

From Morocco, Mr Mohamed claims that he was taken to the “Dark Prison”, a CIA interrogation centre near Kabul in Afghanistan, and then in 2004 to Guantanamo Bay.

MI5 told an ISC inquiry into rendition that it regretted “not seeking proper full assurances” about the use of information it passed to the US about Mr Mohamed. His lawyers argue that the British Government has information about his interrogation and rendition which would help to corroborate his case.

The Government refuses to say what information it holds but has told Mr Mohamed's lawyers it is not obliged to hand over any material.

The application for a judicial review of the refusal to release documents is supported by the US military counsel appointed to defend Mr Mohamed before the Guantanamo Bay tribunal.

Lieutenant-Colonel Yvonne Bradley said: “I have been charged with defending Mr Mohamed to the best of my ability. I cannot pretend that the US military commissions are fair, but how can we possibly hope to help Mr Mohamed if his own Government leaves him to his fate?”

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