Sir William found "corporate failure" at the Ministry of Defence was to blame for the use of banned interrogation methods in Iraq.

BBC: 'Safeguards needed' on interrogation methods

"I'm looking for Jack Bauer at this point, " he said, referring to the character on the popular Fox TV show "24" known for showing unorthodox interrogation methods.

NPR: GOP Hopefuls Hold Debate in South Carolina

In 2008, Mr Brennan was reportedly considered for the top job at the CIA, but he withdrew his name amid criticism, while denying any connection to the interrogation methods.

BBC: Profile: John Brennan

Critics of the Bush administration's interrogation programme say the memos provide evidence that many of the methods amount to torture under US and international law.

BBC: Obama publishes 'torture' memos