This week, one of Parliament's most active bodies, the Joint Committee on Human Rights (JCHR), made up of both peers and MPs, reports on the allegations of government involvement in and knowledge of the torture of terrorist suspects by foreign powers. If you're like me, you find it hard to read anything about torture, but this report is very important because it makes plain these barbaric practices have been commissioned in our name. Those who have read it say it is "truly shocking" and that the government cannot avoid a formal response to the allegations.

I suspect we know much of the detail because of Ian Cobain's exemplary investigation in the Guardian; what Andrew Dismore's JCHR has done is to list all the examples where there appears to be a prima facie case to be answered. And in the absence of a definition of complicity that is accepted across government, the committee defines exactly what the word means.

Does complicity entail actively supplying questions for an interrogation that involves, for instance, water boarding or slicing a man's penis? Being in the vicinity of these actions and encouraging them? Or should we operate on the basis that the knowledge that information being used has been gained from torture is enough to satisfy any decent test of involvement?

I believe it to be the latter for the reason that torture in counterterrorist operations rarely happens independently of a demand for information.

The letter sent to Dismore by David Miliband and Alan Johnson, both of whom refused to appear before the JCHR, leads me to believe that the Foreign Office and Home Office have covered all the bases with various human rights training programmes. "We are confident," they write, "that whenever the issues of torture arises in any of our training courses or internal communications, staff are left in no doubt as to the government's absolute abhorrence of torture."

Absolute abhorrence indeed, but that does not prevent complicity, as Cobain has amply demonstrated. It seems certain that the British government steeled itself against any feelings of revulsion and used as much torture "intelligence" as it could lay its hands on, with agencies crossing the line into brutal collusion. "The government has repeatedly denied that it condones torture," wrote lords Ashdown, Howe, Hannay, Lester, Baroness D'Souza and eight other peers to the Times in March. "The conflict between evidence and the official denial is stark and is undermining the trust in our stated commitment to human rights."

The British state is institutionally hypocritical on torture. Tony Blair says he condemns it and has never authorised it and even though he did know that information being used came from the torture, somehow his spokesman has contrived to finesse his position into a state of innocence. Before Blair, the former home secretary Jack Straw denied authorising torture, but then suggested that the product of the torture chamber might have its uses. As he told the Intelligence and Security Committee in November 2004: "It does not follow that if it [information] is extracted under torture, it is automatically untrue. But there is a much higher probability of it being embellished." Feline as ever, he touches on the critical double standard, which is this: while British courts will have nothing to do with evidence gained from torture, the executive is allowed free rein.

In 2005, the law lords ruled against the use of evidence procured by torture in a judgment where Lord Carswell wrote: "Once torture has become acclimatised in a legal system, it spreads like a disease, hardening and brutalising those who have become accustomed to its use." The then senior law lord, Lord Bingham, was utterly clear that torture evidence "was offensive to ordinary standards of humanity and decency".

But later on in the 90-page judgment, Lord Brown supported the executive using such evidence. He wrote: "It has a prime responsibility to safeguard the security of the state and would be failing in its duty if it ignores whatever it may learn."

The possible benefits of torture are thus admitted and the ground laid for complicity. That British agencies are willing to accept such information, and have supplied lines of interrogation in the past must mean that the use of torture is stimulated, which is a form of complicity. It is not good enough to protest that we are simply the recipients of information that has been extracted by people over whom we have no control.

That excuse doesn't work in other areas of the law. Download pictures of child pornography and you will find yourself facing a prison sentence because even though you did not take part in the abuse and had no control of the abuser, your action effectively added to the demand for the pictures and is held by the law to be part of the stimulus to an appalling crime.

Once the passive involvement is permitted, the state and its agencies pretty soon become active collaborators in torture, although they obviously take care to do this secretly. All the cases listed by the JCHR make our role in torture utterly clear and underline that Britain, a signatory to the United Nations Convention Against Torture, is almost certainly in breach of international law.

Quite apart from the erosion of our own standards and the way this must affect the moral well-being of a society, how on earth can we expect our views about human rights to carry any weight with, for instance, the Chinese over their treatment of the Tibetans, with the Russians or the Burmese junta? It is preposterous that Britain still presents itself to the world as a paragon of virtue when our people have been sitting with their fingers in their ears as some poor bastard has his fingernails ripped out, waiting for a lull in the screaming so they can ask the next question.

It is not just in a legal system that torture spreads like "a disease hardening and brutalising" people. It is time that we learnt exactly what has been going on and what current practices are. The questions in the JCHR report must be answered, but evidently we cannot rely on this government for the truth. As the peers' March letter to the Times stated: "Only a full independent inquiry will meet the need in a democracy to hold accountable those who knowingly breach national and international law."