WATER-BOARDING: doesn't sound too bad, does it? A bit like surfing or bumming around on sun-kissed beaches. But for our knowledge that it's the name used by the CIA to torture al-Qaeda suspects, it might have remained a bland description of a jolly activity. The reality is different, and anyone who has read Eric Lomax's intensely moving memoir The Railway Man knows exactly what it entails. Lomax was a prisoner of the Japanese in Burma during the second world war and he was given the so-called "water cure" when his captors suspected that he was in possession of a secret radio.

This is what they did to him. His torturer tied him to a bench and produced a hose which was turned on in the direction of his face. "Water poured down my windpipe and throat and filled my lungs and stomach. The torrent was unimaginably choking. This is the sensation of drowning, on dry land, on a hot dry afternoon. Your humanity bursts from within you as you gag and choke. I tried very hard to will unconsciousness but no relief came."

Lomax lived to tell the tale. As for the perpetrators, around 2000 of their number were executed by the allies after the war. Among them was Lomax's torturer, Captain Matsuo Komai of the Japanese Imperial Army, who was tried and then executed in Singapore after being found guilty of committing war crimes against allied prisoners-of-war.

Quite right, you might say. Japanese soldiers of his kind had an unenviable reputation for casual brutality. Now, thanks to the release of secret US intelligence documents, we know that the practice used by Komai and others of his ilk is still alive and kicking courtesy of Uncle Sam. It was one of the "enhanced techniques" authorised at Guantanamo Bay where Abu Zubaydah and Khalid Sheikh Mohammad, both leading al-Qaeda suspects, were detained in 2002. Between them they were water-boarded an astonishing 266 times, and that's not all: approval for this vile practice went all the way up to the Oval Office.

By way of return it achieved little. Neither man cracked under pressure and according to the briefings: "KSM produced absolutely no actionable intelligence, he was trying to tell us how stupid we were."

Precisely. Extreme torture is more or less useless for uncovering accurate intelligence. It usually results in escalation which is equally unproductive and it often leaves physical scars which are evidence that torture has been used in the first place. Just as bad, it diminishes those who practise it. Anyone who causes unnecessary physical or mental pain to a helpless human being is never going to win the moral high ground. Not only do they reveal themselves as weak, sadistic and evil-minded but they cut the foundations from the side they represent. Torturing two Arab suspects reveals a similar mindset to those who plant roadside bombs: never mind the means, it's the end that always matters.

Predictably the revelations have caused consternation in Washington. There have been calls for the perpetrators to be prosecuted as war criminals, just as Komai was in Singapore in 1946, but these have been balanced by apologists including former vice-president Dick Cheney, who argues that water-boarding revealed priceless intelligence. As evidence, he cites the fact that since the 2001 attacks the US homeland has remained inviolate and that the war against terrorism is being won.

It's a lousy argument. Cheney was determined to prove that there was a link between al-Qaeda and Saddam Hussein but despite the water-boarding, the sleep deprivation and the infliction of pain, that connection has never been established for the simple reason that it didn't exist in the first place. You can torture a person for as long as you like but if they don't have any information to give you it's a waste of time and effort. All they might do is tell you what you want to hear and that's equally worthless.

But there is something far worse going on here. From the papers made available to the Senate Intelligence Committee, it is apparent that the Bush regime made violence a first resort in its treatment of captured suspects. From Guantanamo Bay, where the Geneva Convention was ignored, to the practice of extraordinary rendition, where people simply disappeared, representatives of the US embraced torture with an enthusiasm that would not have been out of place in Cambodia or North Korea. In so doing, to the dismay of those who respect the US for its many virtues, we in the West suddenly became as bad as the enemy.