Jane Mayer's new book, The Dark Side, reveals in greater detail the utter depravity of the Bush administration's official policy of torture. Mayer's long investigation makes clear that the tactics employed by the CIA on suspected al-Qaida terrorists do not exist in some grey area protected by the euphemism "enhanced interrogation techniques". They are unquestionably torture. It is all the more shocking then that John McCain, knowing all that he does about torture past and present, would sacrifice his considerable personal credibility and vote to preserve the CIA's ability to torture detainees.

Waterboarding has been the focus of attention since confirmation from the agency's director, Michael Hayden, that it had been used on at least three al-Qaida detainees. The ancient technique that forces water into the lungs of a subject but stops just before he dies had previously been prosecuted by the United States as a war crime but now found its way into the "enhanced interrogation" programme authorised by the justice department and employed by the CIA. Hayden and attorney general Michael Mukasey said waterboarding was not currently being used but categorically did not rule out its use in the future.

That would be troubling enough, but what Mayer's book makes clear is that waterboarding was only a small part of the CIA's torture programme. In fact, even detainees that were subjected to waterboarding did not think it was the worst technique they had to endure. That was reserved for stress positions. These were often employed differently but included being shackled to the ceiling of their cells, forcing all the weight of their body onto their shoulders as they were suspended upright for eight hours. One detainee was locked in a box half his size for hours at a time. Most of them were deprived of sleep and bombarded with loud music and noises for 24 hours.

There has always been a troubling level of indifference to these activities, because these are al-Qaida terrorists responsible for the deaths of thousands of Americans. Rage and anger is understandable, but I hope people inclined toward this viewpoint appreciate that one of the principle divisions between us and our enemies is that we hold ourselves to a higher standard, we take our humanity more seriously and we intend to live up to our moral obligations. The United States should not torture prisoners in its captivity, no matter how grave their crimes.

Another rationale often used to condone such tactics is that they are needed to get information out of these detainees that could save American lives. It is vital that we are able to use interrogation to uncover information about our terrorist enemies. If that is in fact the objective, I have never been able to understand why that would lead anyone to think torture is the way to go. Torture is a poor instrument to produce reliable information. It is exceptionally good at producing false confessions. Perhaps it is not surprising then to learn that the Bush administration got some of its techniques from a 1957 US military report about Chinese interrogations during the Korean war titled "Communist attempts to elicit false confessions from Air Force prisoners of war."

John McCain knows this. In 2005, he said that he mourned "what we lose when by official policy or by official negligence we allow, confuse or encourage our soldiers to forget ... that which is our greatest strength: that we are different and better than our enemies." He has repeatedly said: "Torture doesn't work." He described waterboarding as, "not a very complicated procedure. It is torture."

Armed with these core beliefs, McCain led the congressional effort to require that the US military only use interrogation techniques included in the US army field manual on interrogation, a public document that has been approved as lawful by numerous authorities. After its passage, McCain said of a recent trip to a US prison in Iraq that an "army general there said that techniques under the army field manual are working and working effectively, and he didn't think they need to do anything else." It seemed, with Americans dying every day during an extremely complex, multi-sided conflict in which good intelligence was vital to saving lives, the field manual was working.

But that was senator McCain. Now he is running for president and things are a little different. In the wake of the reported success of the field manual in Iraq and Hayden's admission, several US senators attempted to force the CIA to follow the same standard as the military and only use techniques in the field manual. Several senators, that is, except John McCain. Even while reiterating his objections to waterboarding, he voted against the bill that narrowly passed but did not survive the president's veto.

If you had been living on another planet for the last six years you might be able to make a convincing case that the CIA needs to have more flexibility than the military during interrogations. But Jane Mayer has just told us again what that flexibility actually means: torture. Of course McCain knows this too. Unfortunately he has more important things to do, like running for president.