A former head of MI5 has claimed that US intelligence agencies deliberately concealed their mistreatment of terror suspects.

Baroness Manningham-Buller said she learnt that Khalid Sheikh Mohammed, the mastermind behind the 9/11 attacks, had been waterboarded only after she retired from the Security Service in 2007.

In a speech to the Mile End Group at the House of Lords, Lady Manningham-Buller said: “The Americans were very keen that people like us did not discover what they were doing.”

She said that she had wondered, in 2002 and 2003, how the US had been able to supply her service with intelligence from Mohammed.

“I said to my staff, ‘Why is he talking?’ because our experience of Irish prisoners, Irish terrorists, was that they never said anything.

“They said, 'Well, the Americans say he is very proud of his achievements when questioned about it'.

“It wasn’t actually until after I retired that I read that, in fact, he had been waterboarded 160 times.”

Lady Manningham-Buller said that the Government lodged “protests” with the Americans about its treatment of detainees, but refused to elaborate.

She went on to say that the allegations of complicity in torture could disrupt MI5’s work.

“The allegations of collusion in torture and the lack of respect for human rights will wound those individuals personally and collectively, and in some respects – whether proven or not – it will make it harder for them to do their jobs,” she said.

Her remarks come after a series of allegations of British complicity in the torture of terrorist suspects by the US.

It erupted last month after the disclosure of what was described as the “cruel, inhuman and degrading” treatment of Binyam Mohamed, the British resident formerly held at Guantánamo Bay.

Ministers and Jonathan Evans, the current heads of MI5, insisted that there had been no collusion by UK security forces.

But there are enduring questions about exactly when they learnt that the US apparently changed its rules on torture after the 9/11 attacks.

The security services are also under pressure over claims that they have a “culture of suppression” about such matters.

(Source: "Laura Pitel", Baroness Manningham-Buller: US concealed torture from MI5", TimesOnline, 10 March 1020