Downing Street today dismissed George Bush's claim that waterboarding is not torture after the former president used his memoirs to play down the brutality of the interrogation technique and claimed that it saved British lives.

Waterboarding, which was banned by President Barack Obama, helped foil attacks on Heathrow airport, Canary Wharf and a number of US targets around the world, according to Bush.

In Decision Points, published today, Bush insists the practice – which simulates drowning – is not torture, describing it instead as one of a number of "enhanced interrogation techniques".

But Downing Street confirmed the British government still shared Obama's opinion that waterboarding constitutes torture. "It comes under that definition in our view," a No 10 spokeswoman said.

The former chair of the Commons intelligence and security committee, Kim Howells, cast doubt on Bush's claim that it had helped save British lives. "We are not convinced," said the Labour MP.

In an interview with the Times, Bush said: "Three people were waterboarded and I believe that decision saved lives."

Asked if he had authorised the use of the technique in the interrogation of Khalid Sheikh Mohammed, the self-proclaimed mastermind of the 9/11 attacks, Bush answered: "Damn right!"

"We capture the guy, the chief operating officer of al-Qaida, who kills 3,000 people. We felt he had the information about another attack.

"He says: 'I'll talk to you when I get my lawyer.' I say: 'What options are available and legal?'"

In his memoir, Bush writes that waterboarding was highly effective, providing "large amounts of information".

"No doubt the procedure was tough, but medical experts assured the CIA that it did no lasting harm," he writes. "I knew an interrogation programme this sensitive and controversial would one day become public. When it did, we would open ourselves up to criticism that America had compromised our moral values. I would have preferred that we get the information another way. But the choice between security and values was real.

"Their interrogations helped break up plots to attack American diplomatic facilities abroad, Heathrow airport and Canary Wharf in London, and multiple targets in the United States."

The technique was first approved for Abu Zubaydah, an al-Qaida figure arrested in Pakistan in 2002 who was suspected of involvement in a plot to attack Los Angeles International airport.

"His understanding of Islam was that he had to resist interrogation only up to a certain point," Bush writes. "Waterboarding was the technique that allowed him to reach that threshold, fulfil his religious duty, and then co-operate."

Waterboarding is one of a number of controversial practices banned by Obama since he succeeded Bush. The new president has denounced the practice as torture.

Bush refused to accept that definition. "The lawyer said it was legal," the former president told NBC's Today programme. "He said it did not fall within the anti-torture act. I'm not a lawyer. But you gotta trust the judgment of people around you, and I do."

Asked about allegations that lawyers had been pressurised into giving the president the answer he wanted to hear, Bush directed his critics to read the book. He gave an identical response when NBC interviewer Matt Lauer asked him whether it would be legal for another country to waterboard a captured US solider.

While Obama has said the US is no safer as a result of waterboarding and other forms of torture, Bush insisted: "Using those techniques saved lives. My job was to protect America. And I did."

He writes that waterboarding would have been used on more prisoners if the right people had been captured.

"Had we captured more al-Qaida operatives with significant intelligence value, I would have used the programme for them as well."

The claim that waterboarding prevented London attacks was challenged by Howells, . He told BBC Radio 4's Today programme that there had been and still were "real plots", but added that "we're not convinced" that waterboarding produced information which was "instrumental in preventing these plots coming to fruition and murdering people".

Howells said Bush was trying to "justify what he did to the world", a viewpoint echoed by the former shadow home secretary David Davis.

Davis told Today that although security information provided from abroad would have to be used regardless of how it was obtained, torture did not work and should be discouraged.

"People under torture tell you what you want to hear," he said. "You'll get the wrong information and ... apart from being immoral, apart from destroying our standing in the world, and apart from undermining the way of life we're trying to defend, it actually doesn't deliver."