The transport secretary has revealed that aircraft allegedly operated by the CIA to take prisoners out of the USA landed at airports in Northern Ireland.
Allegations on rendition flights continue
The planes landed at Belfast International and City of Derry airports after January 2001.
Alistair Darling said the government had no information about the flights' purposes as they were "non commercial".
Anti-Iraqi war campaigners said they were used to fly prisoners to states where torture was used.
A total of six US planes linked by campaigners to "extraordinary rendition" used UK airports 73 times since 2001, Mr Darling confirmed.
Campaigners claim to have details of planes used by the CIA to transfer terror suspects to countries where they could be tortured.
Mr Darling confirmed the serial numbers of planes that had landed in the UK matched those on the campaigners' list.
But he said he had no evidence they were involved in rendition.
US Secretary of State Condoleezza Rice has denied the US uses torture, but insisted the practice of extraordinary rendition was not unlawful, adding: "Renditions take terrorists out of action, and save lives."