Charles Kennedy today grilled the prime minister over allegations that British airports are being used by the CIA to transport terror suspects to camps where they face torture.
The Liberal Democrat leader was speaking after US secretary of state Condoleezza Rice this week admitted that so-called "rendition flights" had long been used to transport suspects around the world.
But while she did not deny the existence of secret camps where these suspects would be held, she rejected outright suggestions that they would face torture, saying the US condemned the use of torture in all forms.
Today Mr Kennedy used prime minister's questions in the Commons to ask Tony Blair what he knew about this policy, and about the use of British airports for such flights.
"To what extent has his government co-operated in the transport of terrorist suspects to Afghanistan and elsewhere, ostensibly for torture purposes?" he asked.
Mr Blair replied that he had no knowledge of such flights using British airports to re-fuel, but said he know about the use of rendition flights, because they had long been a part of US policy.
Torture was an entirely separate matter, however, and the prime minister condemned this absolutely. He also accepted Ms Rice's assurance that the US was conducting itself in accordance with international conventions on torture.
"It is just as well to remember that some of the people we are talking about are people we need to detain for actions of international terrorism, some of whom are extremely dangerous and some of whom provide information of fundamental importance," he said.
"But of course they [receive] proper treatment. US policy on this has been clear for ages, it is not a matter of contention and what Secretary of State Rice said yesterday I fully endorse."
Ms Rice's comments came after increasing pressure to clarify the allegations of the CIA flights. Foreign secretary Jack Straw last week wrote to Washington on behalf of the EU to demand an explanation.