George Tenet, the former CIA director who masterminded the interrogation of terror suspects after the September 11, 2001, attacks, broke his silence last night and said that “enhanced” techniques such as simulated drowning were not only justified, but worked.

Mr Tenet, who became head of the CIA in 1997 and resigned in June 2004, was asked by CBS television about the techniques used against high-value terror suspects. The programme used “enhanced” techniques that included sleep deprivation, exposure to extreme temperatures and water boarding, in which suspects were reportedly restrained as a steady stream of water was poured over their faces, causing a severe gag reflex and a terrifying fear of drowning.

The practices have been condemned by many international observers, who say that they run foul of the Geneva Conventions governing the treatment of prisoners of war.

Mr Tenet, publicising his much anticipated memoir, At the Centre of the Storm, on the 60 Minutes programme, said: “Here’s what I would say to you, to the Congress, to the American people, to the President of the United States: I know that this programme has saved lives. I know we’ve disrupted plots.

“I know this programme alone is worth more than the FBI, the Central Intelligence Agency and the National Security Agency put together have been able to tell us.”

The techniques of “enhanced” interrogation were introduced after the 9/11 attacks, at a time when Dick Cheney, the Vice-President, said that prosecuting the War on Terror would entail moving to the “dark side”.

When pressed by CBS about whether interrogations included water boarding, Mr Tenet refused to talk about techniques, and insisted that what he meant by “enhanced interrogation” did not amount to torture.

“We don’t torture people,” Mr Tenet said. “The context is it’s post-9/11. I’ve got reports of nuclear weapons in New York City, apartment buildings that are going to be blown up, planes that are going to fly into airports all over again, plot lines that I don’t know. I don’t know what’s going on inside the United States, and I’m struggling to find out where the next disaster is going to occur.

“Everybody forgets one central context of what we lived through: the palpable fear that we felt on the basis of the fact that there was so much we did not know.”

When Khalid Sheikh Mohammed, the September 11 mastermind, was captured in a raid in Pakistan in March 2003, Mr Tenet said the techniques were apparently a surprise to him. The captured terrorist told CIA interrogators: “I’ll talk to you guys when you take me to New York and I can see my lawyer.” Instead, he was reportedly flown around the world, kept in secret prisons and water- boarded. In a closed hearing at Guantanamo Bay this year, Mohammed claimed that he had been tortured by the CIA. There is no evidence to corroborate the claim.

Asked whether he lost sleep over the interrogations, Mr Tenet said: “Of course you lose sleep over it. You’re on new territory.”

Times Recommends

• The Japanese Prime Minister is doomed: or is he?
• Brighton company 'involved in cyber attack'
• The art of survival: it's all in the mind