NEW YORK - US Republican presidential front-runner Donald Trump on Monday slammed CIA Director John Brennan after the spy agency chief said over the weekend that he would not use waterboarding or other torture techniques, even if the next president orders him to do so.

The billionaire businessman said the comments of the top intelligence officer are “ridiculous,” and said any refusal to employ all the available tools to stop terrorists undermines national security.

“I mean, they chop off heads and they drown people in cages - with 50 in a cage in big steel, heavy cages, drop them right into the water,” he said in a phone interview with Fox News. They “drown people - and we can’t waterboard and we can’t do anything.”

While the CIA used waterboarding and other methods to interrogate terrorist suspects in the wake of the September 11th, 2001, attacks, a Senate report in 2014 found that the practice was not only ineffective - it failed to uncover “imminent threat” intelligence - but was often counterproductive.

President Barack Obama signed an executive order within a few days of taking office in 2009 banning enhanced interrogation techniques.

In an NBC News interview Sunday, Brennan adamantly disavowed the use of enhanced interrogation tactics, and said the CIA would disobey any White House order to use them on a suspect.

“I will not agree to carry out some of these tactics and techniques I’ve heard bandied about because this institution needs to endure,” Brennan said. “Absolutely, I would not agree to having any CIA officer carrying out waterboarding again.”

Waterboarding and other enhanced interrogation tactics have been labelled torture - and thus, in violation of international law - by critics, who also say they’re an ineffective means of obtaining actionable intelligence from terror suspects.

Trump has been criticized for his stance on torture since February, when he said he would order waterboarding “and a hell of a lot worse” in the fight against the Islamic State group.

Senator Ted Cruz, meanwhile, said he does not believe waterboarding qualifies as torture, and supports it and other enhanced interrogation methods in the name of national security.

Senator John McCain, a Republican, who was reportedly tortured as a prisoner of war in Vietnam, called both Trump and Cruz’s judgement into question, while former CIA Director Michael Hayden has said the would-be commanders in chief would be met with total rejection if they tried to force CIA officers to take part in such activities.

“If any future president wants [the] CIA to waterboard anybody, he better bring his own bucket, because CIA officers aren’t going to do it,” said Hayden, who also served as the head of the National Security Agency. "Multiple investigations, grand juries, presidential condemnations, and congressional star chambers have a way of doing that to you."