Bob Stewart, Britain's senior Conservative MP and former Army officer, has admitted he had been "kind of a torturer" when he was posted to Northern Ireland.
The former Army colonel said that he believes torture is sometimes "justified" and can work as an interrogation method.
Describing how during The Troubles he had shown "people pictures of their friends that had been blown up", he said: "Technically as you look at it today I was a kind of a torturer.
"Of course it was acceptable then. It's now unacceptable and now it's defined as torture."
Mr Stewart, who completed seven operational tours of Northern Ireland during The Troubles, was speaking after US President Donald Trump used his first television interview since coming to office to indicate his support for waterboarding.
The Conservative MP said he opposed waterboarding, but techniques such as sleep and food deprivation could be acceptable in certain situations.
"We don't like torture. No one likes torture. Not even Trump likes torture," Mr Stewart told BBC 5 Live. "But the fact of the matter is... sometimes it might work, and sometimes it might be justified.
"I don't agree with waterboarding, but a certain amount of persuasion might be justified if someone for example had the knowledge about where a nuclear weapon that was going to explode in London was.
"That is where I suggest that people might say a certain amount of persuasion could be justified. I'm qualifying it all the way through.
"In circumstances where a great number of people, or indeed one person, is going to be killed, you have to think very carefully about what pressure you can put on people in order to give that information to stop peoples' lives being lost."
Asked about the types of torture techniques that might be suitable in those situations, he replied: "Sleep deprivation. Lack of food. Perhaps, as I've done, showing people pictures of their friends that have been blown up. That sort of thing."
Mr Trump is understood to be preparing to order a review of interrogation methods and the possible reopening of "black site" prisons outside the US.