The metropolitan police are to investigate MI6, the secret intelligence service, over alleged complicity in the torture of a terror suspect, in the second criminal investigation of the conduct of British intelligence officers in the war on the terror to be announced this year.

Now there are calls for a full public inquiry into the activities of the security and the intelligence services in their joint operations with the CIA.

Police have already begun an investigation into MI5's possible complicity in the alleged torture of the British resident and former Guantanamo inmate Binyam Mohammed.

It is understood that MI6 referred the second case to the Attorney General, Baroness Scotland, after a review of its joint operations and intelligence-sharing with the CIA in connection with the interrogations of several terror suspects, many of whom have been or are still being held at Guantanamo.

The Foreign Office and the Metropolitan Police declined to name the second man at the centre of the inquiry, but speculation has centred on Abu Zubayda, the Saudi-born al-Qai'da leader subjected to beatings and waterboarding by the CIA.

Last month, the US Attorney General, Eric Holder, announced a criminal investigation into the interrogation techniques used by the CIA. MI6 were known to be interested in Zubayda because of his links to British terror cells. Any report published by the US government may incriminate British officers who worked with the CIA.

Scotland Yard said Baronness Scotland, asked it to investigate "the conditions under which a non-Briton was held" and the "potential involvement of British personnel".

Clara Gutteridge, the Secret Prisons and Renditions Investigator at the human rights charity, Reprieve, said: "By blaming a few bad apples, the British Secret Services are allowing government ministers to avoid responsibility for crimes committed under their watch. It is highly suspicious that the government still refuses to publish its guidelines to agents [on dealing with evidence of torture] from the period in question. Sadly, it seems that only a full public inquiry will force our government to come clean on these allegations."

Only last month, Sir John Scarlett, the head of MI6, said there was "no torture and no complicity in torture" by SIS officers. A Metropolitan Police spokesman said: "We can confirm that the Attorney General asked the Metropolitan Police to investigate a case that was a referral from the Secret Intelligence Service. The police said that the case was unrelated to the ongoing investigation into MI5's complicity in the alleged torture of Binyam Mohamed.

Victims of the war on terror? The allegations

Shaker Aamer

British resident who accused MI6 of complicity in his torture when he was held by the Americans in Afghanistan in 2002. He alleges that MI6 officers were present during his torture which he alleges includes having his head banged against a wall. He is still being held in Guantanamo Bay despite the British government's request for his release.

Mustafa Setmarian Nasser

A Spanish citizen of Syrian origin, held by the US on suspicion of terrorist activities. Mustafa Nasar was seized in Pakistan in 2005 and handed to US forces. He was then secretly flown to the British Overseas Territory, Diego Garcia and almost certainly held there. Since then, he has disappeared. He has links to Britain and may have been questioned by MI6 officers.

Abu Zubayda

A Saudi-born al-Qai'da leader who was subjected to beatings and waterboarding by the CIA. He is accused of helping to recruit agents in the UK and may have been interrogated by MI6 officers. Eric Holder, the US Attorney General, is looking at possible criminal charges against the CIA officers. His report could implicate MI6.

Source: Independent

Belfast Telegraph