Last year Jack Straw, Labour's Foreign Secretary in 2004, told a radio interviewer: "We were opposed to unlawful rendition.

We were opposed to any use of torture or similar methods. Not only did we not agree with it, we were not complicit in it and nor did we turn a blind eye to it."

Those words may have come back to haunt him yesterday when a BBC documentary claimed that the UK Government approved the rendition to one of Colonel Muammar Gaddafi's notorious prisons of a man who would later play a key role in overthrowing the tyrant.

Already there are questions about the role of the British Government and the intelligence services in the rendition and torture of former Guantanamo detainee Binyam Mohamed. Though the Crown Prosecution Service announced in January that no-one from the security services would face charges of collusion, for want of sufficient evidence, its statement supported Mohamed's version of events, which includes the claim that his torturers used information that can only have come from British intelligence sources.

In Scotland there is particular interest in UK complicity in the practice of rendition because of the possible use of Prestwick airport as a refuelling stop during these flights, following an investigation by The Herald in December 2004.

Now the Metropolitan Police is conducting a major investigation into claims that in the same year British spies were involved in the rendition and torture of two prominent opponents of Gaddafi, including Abdel Hakim Belhaj, then leader of the Libyan Islamic Fighting Group (LIFG).

Few can now doubt that MI6 was involved in his rendition to Tripoli, where he says he was tortured for four years. A letter found in the rubble of the office of Gaddafi's intelligence chief, Musa Kusa, not only refers to the "safe arrival" of the "air cargo" (Mr Belhaj) but also claims credit for getting him there: "the intelligence was British". The chummy tone of this communication, from Sir Mark Allen, a senior MI6 officer, is very worrying.

As with the Binyam Mohamed case, the central question is this: given that successive UK governments claim, as Mr Straw did, that they will have nothing to do with rendition or torture, did British spies act unilaterally or were they acting on Government authority, as last night's documentary claimed? If they were, who gave that authority?

In 2004 the LIFG was not a banned organisation. In fact, previously its members had been given quiet encouragement and asylum in Britain and raised funds here. All that changed post 9/11, particularly when Gaddafi started passing himself off as an ally in the "war on terror", and offered to give up his weapons of mass destruction and open up the country's oil and gas fields to Western companies.

While Mr Belhaj was languishing in a cell in Tripoli, Tony Blair was shaking hands with Gaddafi. The LIFC was banned in Britain the following year after claims that it harboured violent extrremists with al Qaeda links. Was that assessment based on confessions obtained under torture in Tripoli? If so, it illustrates the unreliability of such evidence.

There are four points here. First, there is a whiff of hypocrisy in governments that condemn torture elsewhere, but allow it to happen on their watch with nods and winks.

Secondly, the two-faced treatment of men like Mr Belhaj, who in British intelligence eyes has effectively gone from hero to zero and back to hero, can only foment the radicalisation of young Muslims.

Thirdly, this episode should act as a warning against cosying up with despots who claim to have turned over a new leaf.

Finally, let's be clear. The British Government is under a legal and moral obligation not only to condemn torture but to prevent it. If there have been abuses, they must be exposed.