The British government has admitted for the first time that it handed over two "terror" suspects captured in Iraq five years ago to United States agents, who transferred them to Afghanistan for interrogation.
The announcement by John Hutton, the UK's defence minister, came despite previous government assurances to the contrary concerning Britain's involvement.
The pair are still being held in Afghanistan, but the US had promised that they were held in a "humane, safe and secure environment", Hutton said.
"Two individuals were captured by UK forces in and around Baghdad, they were transferred to US detention in accordance with normal practice and then moved subsequently to the US detention facility in Afghanistan," the minister said about the operation in 2004.
Clare Algar, the executive director of Reprieve, a UK-based legal-action charity, said: "This government has misled us again and again. First, they said that Diego Garcia was not used for rendition flights; then they had to admit that they had misled us on that.
"Then they said that the security services condemn torture, yet it seems that those services were complicit in the torture of Binyam Mohamed.
"Now the defence secretary tells us that, despite previous assurances to the contrary, British forces handed prisoners to US forces in Iraq whom the US have rendered to Afghanistan.
"Surely we must immediately have the public inquiry into the government's conduct of the 'War on Terror' demanded by so many."
The two suspects were members of Lashkar-e-Taiba an "organisation with links to al-Qaeda," he said.
"The US government has explained to us that they were moved to Afghanistan because of a lack of relevant linguists necessary to interrogate them effectively in Iraq," Hutton said.
Lashkar-e-Taiba, a Pakistan-based group, has been blamed by India for last year's attacks on Mumbai that killed more than 165 people.
Hutton said it was clear, in retrospect, that the transfer of the two suspects "should have been questioned at the time".
The European parliament has denounced European Union member states who colluded with Washington to help the CIA carry out secret "rendition" flights which transported so-called terror suspects to third countries for interrogation.