Christians have condemned Donald Trump for saying that waterboarding "works" and torture can sometimes be appropriate when it comes to dealing with Islamic State militants who murder Christians in the Middle East.

Speaking to ABC News, the new president said that as long as Islamic State beheads Christians and the US continues to ban torture, "we're not playing on an even playing field".

Trump said: "When they're chopping off the heads of our people and other people. When they're chopping off the heads of people because they happen to be a Christian in the Middle East, when ISIS is doing things that nobody has ever heard of since medieval times, would I feel strongly about waterboarding? As far as I'm concerned, we have to fight fire with fire."

Asked whether he wants to reintroduce waterboarding, Trump said: "I will rely on [CIA director Mike] Pompeo and [defence secretary James] Mattis and my group. And if they don't want to do it, that's fine. If they do want to do it, then I will work toward that end."

He added: "I want to do everything within the bounds of what we're allowed to do if it's legal. If they don't want to do it, that's fine. Do I feel it works? Absolutely I feel it works...I asked [intelligence figures] the question does waterboarding work? And the answer was yes, absolutely."

Peter Dixon, a spokesperson for Action by Christians Against Torture (ACAT), told Christian Today: "ACAT UK very much regrets the suggestion made by President Donald Trump that the US would consider re-introducing waterboarding during the next few months.

"Being realistic it is unlikely to happen because of the likely opposition from within the Senate and the Congress. It is reported that Republican Senator John McCain said yesterday that even if President Donald Trump were to sign an executive order allowing torture, US law is clear on the practice. It also appears that President Trump's Cabinet members, including his defence secretary James Mattis and the CIA Chief Mike Pompeo disagree with the President on this matter.

"We greet this response with gratitude and relief although we cannot disregard the statements of the new president. This matter will be kept under constant review by ACAT worldwide. ACAT UK stands by the UN Declaration of Human Rights when it says in Article 5: 'No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment.' We stand with Archbishop Romero of El Salvador when he said: 'Whoever tortures a human being, whoever abuses a human being, whoever outrages a human being abuses God's image, and the Church takes as its own that cross, that martyrdom.'"

Founder of ACAT Roy Jenkins added: "Torture is always wrong. It is against all international agreements which say it is wrong. The governments of the world have signed up to these almost without exception. Torture is often inflicted on people who have in fact committed no crime. In the international agreements it is simply illegal to commit the assaults which torture involves. It implies that terrorists and tyrants have won, if we resort to the methods of tyranny, because that then means that we adopt their evaluation of human life. And all this is in stark contrast to the Christian understanding: that everyone is made in the image of God...Christians of all people should be sensitive to the fact that what we do to the most vulnerable, we do it to the Christ who was himself tortured to death. It is a complete denial of the Christian understanding and the understanding of people of all faiths and none, that you can treat people in this way."

Steve Chalke, the founder of Oasis Church and anti-slavery charity Stop the Traffik wrote on Twitter: "As Jesus taught, somewhere in here I'm sure, bring on the torture, fight fire with fire'."

Brian Zahnd, pastor of World Life Church, effectively accused Trump of "pretending to be a Christian". He tweeted: "Once you try to reconcile 'love your enemy' with 'torture works', you know you've forsaken Christ and are only pretending to be Christian."