It was a good day to bury bad news. As millions of Americans were glued to the most exciting presidential race in living memory, the Bush Administration admitted publicly for the first time that it had used the simulated drowning technique of waterboarding on terror suspects in its custody.

Past practitioners of waterboarding, which is condemned around the globe as torture, have included the Spanish Inquisitors and the Khmer Rouge. Official confirmation that American interrogators had joined their ranks was almost lost in a blizzard of rolling headlines as the contenders battled through Super Tuesday’s historic “national primary” for their party’s presidential nomination.

Michael Hayden, the CIA director, confirmed the use of waterboarding in congressional testimony, in response to leaked reports that the tactic was used on three al-Qaeda suspects in the two years after the terrorist attacks on September 11, 2001. The admission prompted demands from Democratic senators for an investigation into whether interrogators broke the law.

In his own testimony this week, Michael Mukasey, the new Attorney-General, infuriated Democrats when he refused to define waterboarding as illegal torture. He conceded, however, that if the technique used on him, he “would feel that it was”.

During waterboarding, an individual is strapped down while clothes are placed over the nose and mouth and a stream of water poured over them. The technique simulates the sensation of drowning and induces panic. In extreme cases it may result in death. Its legality rests on the interpretation of Geneva Conventions and a US federal law that prohibits torture.

Mr Hayden told the Senate Intelligence Committee that his agency had used the technique against three of its most important terror suspects, Khalid Sheik Mohammed, Abu Zubayda and Abd al-Rahim al-Nashiri, during 2002 and 2003. “We used it against these three detainees because of the circumstances at the time,” he said. “There was the belief that additional catastrophic attacks against the homeland were inevitable, and we had limited knowledge about al-Qaeda and its workings. Those two realities have changed.”

Waterboarding was banned by Mr Hayden in 2006, but he told senators that the technique remained an option for the CIA if it had the specific consent of the President and legal approval of the Attorney-General.

Yesterday the White House said that the technique could be used again. “It will depend upon circumstances,” Tony Fratto, the White House spokesman, said. “The belief that an attack might be imminent, that could be a circumstance that you would definitely want to consider.”

Congress is considering limiting the CIA interrogation techniques to those that are used by the US Army. Mr Hayden said that any limitations on the CIA “would substantially increase the danger to America”.

John McCain, the Republican front-runner after victories across the country on Super Tuesday, has angered party colleagues with his efforts to curb the use of torture. Democrats have threatened to withhold confirmation of a new deputy attorney-general until the Justice Department takes up the issue of who authorised the waterboarding of the three suspects and whether they broke the law.

In December the CIA was forced to admit that it had destroyed videotapes showing interrogations of Zubayda and al-Nashiri, prompting an investigation by the Justice Department.

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