Lawyers for the last British resident in Guantanamo sued MI5 and MI6 today for defamation.
Legal action charity Reprieve have said Britain's spooks knowingly made false statements about Battersea man Shaker Aamer to his US captors.
Mr Aamer has been held without charge or trial for 11 years, despite being cleared for release in 2007.
His lawyers say he has been tortured and beaten almost every day and they fear for his physical and mental health.
Recently declassified documents seen by the Morning Star giving details of an interview between Reprieve director Clive Stafford Smith and Mr Aamer on September 6 also form part of the action.
In it Mr Stafford Smith refers to a number of allegations which Mr Aamer has been told during interrogations were passed to the US by British spooks and for which he argues there is no evidence.
The British government has repeatedly claimed that it wants Mr Aamer home.
Mr Stafford Smith has said Mr Aamer has told him "that UK agencies are still telling lies about him - lies which prevent him from being released."
Among the allegations are claims that Mr Aamer is a member of al-Qaida who was personally paid by Osama bin Laden, that he was a member of the "London cell of al-Qaida" and that he recruited people in London to travel to Afghanistan to fight.
Mr Aamer is clear that all these claims are wholly false and no independent proof has been brought forward to show otherwise.
A pre-action letter from Reprieve to Foreign Secretary William Hague and Home Secretary Theresa May states that Britain's spooks have been "complicit in Mr Aamer's mistreatment" and have "worked hand in glove" with his captors.
It further states that Mr Aamer has been interrogated over 500 times by US personnel and that these interrogators informed him that the allegations put to him had been passed to them by MI5 and MI6.
His lawyers state: "There is something particularly invidious and indecent about deliberately making false statements in secret when it was forseeable that such statements would be published in the US.
"The consequences are dire: Shaker Aamer remains in arbitrary and indefinite detention almost 11 years after he was originally seized."
The Metropolitan Police is currently investigating claims that Britain's spooks were complicit in Mr Aamer's rendition and torture and that an MI5 agent was present when he was beaten by US interrogators and threatened with death.
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