Arizona senator attacks Rick Perry, Herman Cain and Michele Bachmann for pledge to reinstate technique he says is torture

John McCain, the former Republican presidential candidate, has slammed contenders for next year's election for pledging to reinstate waterboarding of terrorism suspects if they reach the White House.

McCain, a former prisoner of war in Vietnam, has consistently described waterboarding as torture. He said in a tweet on Monday that he was "very disappointed" by support for the technique by Herman Cain, Rick Perry and Michele Bachmann at Saturday's Republican foreign policy debate in South Carolina.

The candidates criticised President Obama for banning the use of waterboarding, and said they would reinstate its use if elected.

McCain tweeted: "Very disappointed by statements at SC GOP debate supporting waterboarding. Waterboarding is torture."

Obama also criticised the Republicans candidates on Monday.

"They're wrong. Waterboarding is torture. It's contrary to America's traditions. It's contrary to our ideals," the president said.

"If we want to lead around the world, part of our leadership is setting a good example. Anybody who has actually read about and understands the practice of waterboarding would say that that is torture. That's not something we do."

Some of the Republican candidates argued that the use of the interrogation method, which simulates drowning, had produce valuable intelligence, and that Obama has endangered American lives by ending its use.

At the debate, Cain said of waterboarding: "I don't see it as torture. I see it as an enhanced interrogation technique."

Bachmann took a similar position. "If I was president I would be willing to use waterboarding," she said. "I want to save American lives and that's why I want the CIA to have every interrogation tool available to them so we can win the war on terror."

On Monday, she repeated her position on Fox News. "No one died from the use of waterboarding. Is it uncomfortable? Yes, it's uncomfortable. But our worry should not be the comfort level of terrorists," she said.

Other Republican candidates, Ron Paul and John Huntsman, described waterboarding as unacceptable. "It's illegal under international law and under our law," said Paul.

The debate produced a backlash against pledges to slash US aid to foreign countries – particularly when Perry said he would reassess the $3bn a year in mostly military assistance given to Israel.

The Texas governor said during the debate: "The foreign aid budget in my administration for every country is going to start at zero dollars."

He said that there should then be a national debate on "whether or not a penny of our taxpayer dollars needs to go into those countries".

Pressed as to whether the freeze on aid would apply to Israel, he said: "Absolutely. Every country would start at zero. Obviously Israel is a special ally, and my bet is we would be funding them at some substantial level. But it makes sense for everyone to come in at zero and make your case."

Romney made a similar statement, although in the context of a question about Pakistan. "One of the things we have to do with our foreign aid commitments, the ongoing foreign aid commitments – I agree with Governor Perry. You start everything at zero," he said.

But even before the debate was over, the candidates' campaign teams were rowing back in the face of concern at alienating Israel's supporters, particularly rightwing Christian voters. They also risked undermining their own positions that Obama is an unreliable supporter of Israel.

The Democrats quickly seized on the issue. The chair of the Democratic National Committee and member of Congress, Debbie Wasserman Schultz, said she was "aghast" at the position taken by Perry and Romney.

"I cannot think of a more irresponsible, risky or deplorable position towards our most important friend and ally," she said. "Mitt Romney and the rest of the Republican field clearly do not understand the vital need for the US to consistently stand by our friend and ally, Israel, and not only when it's politically popular."

The Republican Jewish Council drew Perry's attention to the "10-year Memorandum of Understanding that governs US-Israel funding levels" by guaranteeing they will continue.

Bruce Riedel, a former presidential assistant and director of Near East affairs on the National Security Council, said that the Israeli military would not be able to do long-term planning because it would not know what assistance it was to receive from the US from one year to the next.

"[It] would have a very disruptive impact on Israeli military planning and Israeli security. Perry's idea is bad news for Israel and shows how little he understands its needs," Riedel wrote on the Daily Beast.

Perry's campaign released a statement after the debate describing him as "a friend to Israel" who "understands the challenges faced by the country," which is "a unique and vital political and economic partner for the United States."

Romney's campaign later tried to say that he was referring only to Pakistan, but his answer appeared to address foreign aid in general. It went further on Sunday, saying that he would increase aid to Israel if elected.

The question of aid to Israel can be treacherous territory for rightwing Republicans. Many of their supporters are instinctively isolationist and against aid to foreign countries, particularly those they regard as corrupt or questionable friends to the US. But they are also often fervent supporters of military support for Israel.

Proposals by some on the right that aid to Israel be separated out from other foreign assistance have received a cool reception from lobby groups such as the American Israel Public Affairs Committee (Aipac), which are concerned that Israel should not be seen to be getting special treatment.

• This article was amended on 16 November 2011. The original attributed a quote on waterboarding at the debate to Rick Perry. This has been corrected.