Ex-MI5 head: US concealed torture

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

Her intervention, to a selected gathering at the House of Lords, followed intense controversy over British agents' alleged collusion with US counterparts employing torture techniques.

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 Guantanamo Bay.

Ministers and current MI5 chief Jonathan Evans have insisted there was 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. But Lady Manningham-Buller said it had been the US that had been "very keen to conceal from us what was happening".

She added: "The Americans were very keen that people like us did not discover what they were doing."

In a lecture at an event organised by the Mile End Group, she said she had wondered, in 2002 and 2003, how the US had been able to supply the UK 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," she said.

"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 the Government had 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.