Ukip leader Paul Nuttall has said he would "probably" support the use of waterboarding if it saved lives.
Mr Nuttall made the remarks in the wake of US President Donald Trump's apparent willingness to revive the use of torture techniques, including waterboarding in which suspects are subjected to simulated drowning.
Prime Minister Theresa May said the UK would not shift from its condemnation of torture.
But speaking on the by-election campaign trail in Cumbria, Mr Nuttall said: "I think sometimes you have to fight fire with fire.
"I think that these people are incarcerated because they are bad people and they want to do us harm, and if waterboarding ensures that it saves a number of lives in this country, or America, because someone admits to something that is going to happen in terms of a terrorist attack then through gritted teeth I probably would be OK with that."
When Mr Trump was asked about the use of torture in his first TV interview as President, he said: "Absolutely, I feel it works."
A draft presidential order made public this week envisages a review of interrogation methods for terror suspects, the possible reopening of "black site" prisons outside the US and the continued use of the Guantanamo Bay camp in Cuba to hold "enemy combatants".
On Friday, Mr Nuttall visited the constituency of Copeland to open the party's campaign office and support its candidate, local NHS worker Fiona Mills.
He is standing for election himself on February 23 in the Stoke-on-Trent Central by-election but denied that meant Ukip had less chance of winning in Copeland.
He said: "No, I think we have got an excellent candidate here. I think she is perfect, she is our Cumbria chairman and she has an outstanding history working for the NHS. She is a good local candidate and we are going to campaign hard.
"I am not going to second guess anything that the British public will do these days after Brexit and we have seen what is going on in the Western world, we have seen the election of President Trump.
"But what I will say is that I genuinely believe we will improve on our general election result and we are going to give it a damn good go."
On the subject of Brexit, he said that Labour was "all over the place".
He said: "The problem that Labour have got is the majority of Labour voters want to leave the EU and voted to do so but in their heart of hearts the Labour Parliamentary Party want to remain and want us to stay in the EU, and now they are going to split all over the place.
"The one thing that is clear at the moment and will become even more clearer is that you can't trust Labour with Brexit."
On Labour accusations that he is a supporter of NHS privatisation, he said: "Labour privatised 5% of the NHS when they were in power and saddled the NHS with a £80 billion debt through crazy PFI (private finance initiative) contracts.
"Do you really think I am going to be lectured to or hectored by Labour when it comes to the NHS. Yes they founded it but they have become an abusive parent when it comes to the NHS.
"We do not want to privatise the NHS. We want to keep it public and we are the only party who want to put money into the NHS and can tell you where that money will come from.
"We will do it by slashing the foreign aid budget which is costing the British people £30 million every single day."
Jamie Reed, the former Labour MP for the seat, prompted the by-election when he resigned to take up a position at Sellafield nuclear power plant.
He held Copeland with 16,750 votes (42%) in 2015, ahead of the Conservatives on 14,186 (36%), Ukip on 6,148 (15%) and the Liberal Democrats on 1,368 (3%).
Meanwhile, Conservative MP Bob Stewart sparked a political storm on Thursday when he argued torture was sometimes "justified" and could work as an interrogation method.
The former Army officer said he had been "kind of a torturer" when he served in Northern Ireland during The Troubles.