An American expert in torture techniques has denounced his government for allowing "waterboarding" to be practised against terror suspects, just as a graphic advertisement showing the brutal reality of the technique is unveiled to British cinema-goers.
Malcolm Nance, who trained hundreds of US servicemen and women to resist interrogation by putting them through "waterboarding" exercises, demanded an immediate end to the practice by all US personnel.
He said: "They seem to think it is worth throwing the honour of 220 years of American decency in war out of the window. Waterboarding is out-and-out torture, and I'm deeply ashamed President Bush has authorised its use and dragged the US's reputation into the mud."
Mr Bush faced criticism recently when he vetoed a Bill that would have outlawed such methods of "enhanced interrogation" – the White House refuses to describe it as torture.
Mr Nance said: "You have a purpose-built table with straps in a pattern so that people can be strapped and unstrapped quickly. The head is strapped down in such a way so they cannot resist the water. The head is elevated so the water goes down the oesophagus.
"The water is poured very carefully over the nose – you keep a constant pour. You are drowning in water but you don't have the ability to hold your breath. You feel the water going in, you understand that water is filling your lungs."
Mr Nance, who is now an independent consultant, said the technique was also futile, as well as barbaric, as the prisoner would say anything to survive – regardless of its truth.
Amnesty International is leading the campaign to persuade the US to abandon the practice – a form of torture used as long ago as the Spanish Inquisition – and is stepping up its efforts with the release of a graphic and disturbing advertisement.
The broadcast begins with images of glistening clear liquid, suggesting it could be promoting a new brand of vodka or gin. But the camera pulls back to show water is being poured over the face of a desperate man strapped to a table.
Kate Allen, the UK director of Amnesty International, said: "Our film shows you what the CIA doesn't want you to see – the disgusting reality of half-drowning a person.
"For a few seconds, our film-makers did it for real. Even for those few seconds, it's horrifying to watch. The reality – in a secret prison with no one to stop it – is much, much worse."
The advertisement can be seen at www.unsubscribe-me.org from today and at 50 cinemas from next month onwards.
The Bush administration insists it does not torture people, but says it uses "enhanced interrogation techniques", which, according to critics, for all intents and purposes include torture.
When pressed on the issue, George Bush has repeatedly denied subjecting people to torture. At a press conference in Panama in 2005, the US president told reporters: "We do not torture people." He said the US would aggressively pursue terrorists, but it would do so under the law.
In an interview with CBS in 2006, Bush again denied the use of torture when asked about secret CIA prisons or "black" sites around the world.
"We have to have the capacity to interrogate - not torture - but interrogate people to learn information," he said.
What constitutes torture?
Under a 1994 UN convention, torture means "any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted" to obtain information.
The convention has been ratified by 136 countries including the US. The UN explicitly banned torture after the second world war, when its general assembly included a prohibition against torture in the landmark universal declaration of human rights.
Article 5 states: "No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment."
Because it has signed up to treaties banning torture, the US goes to extreme lengths to deny it tortures prisoners, while getting into legal contortions as to what constitutes torture or not.
What has been documented?
There is plenty of documentation on what US interrogators have done. The FBI released a report last year in which FBI officials reported 26 cases of possible mistreatment by law enforcement or military personnel at Guantánamo Bay.
The report revealed captives were chained hand and foot in a foetal position to the floor for 18 hours or more, where they urinated and defecated on themselves.
Besides being shackled to the floor, they were subjected to extreme temperatures, with the air conditioning either turned close to freezing or turned off so that room temperatures topped 38C (100F).
In 2006, the vice-president, Dick Cheney, told a radio interviewer that waterboarding - the near-drowning of a captive - was used on the alleged September 11 mastermind Khalid Sheikh Mohammed at Guantánamo.
Cheney said the use of waterboarding on Mohammed was "a no-brainer for me. But for a while there, I was criticised as being the vice-president for torture. We don't torture. That's not what we're involved in."