Prime Minister David Cameron has challenged former US President George Bush's claim that the use of waterboarding saved British lives.
In his book Decision Point, published this week, Mr Bush said that the use of the technique - a kind of simulated drowning - on terror suspects "helped break up plots" to attack Heathrow and Canary Wharf.
Mr Bush vigorously defended the use of waterboarding and denied it amounted to torture, as critics and some allies claim. The British Government has long regarded it as a form of torture.
Asked whether US use of waterboarding had prevented attacks in the UK, Mr Cameron said: "Look, I think torture is wrong and I think we ought to be very clear about that. And I think we should also be clear that if actually you're getting information from torture, it's very likely to be unreliable information."
And the Prime Minister suggested that the use of torture - and the incarceration of suspects in Guantanamo Bay without trial - could be counter-productive, by encouraging support for terrorists.
Speaking during a round of broadcast interviews in Seoul, Mr Cameron said: "I think there is both a moral reason for being opposed to torture - and Britain doesn't sanction torture - but secondly I think there's also an effectiveness thing about what he said.
"Thirdly, I would say if you look at the effect of Guantanamo Bay and other things like that, long-term that has actually helped to radicalise people and make our country and our world less safe, so I don't agree."