A criminal inquiry would be a deep embarrassment for the Government, which has repeatedly denied turning a blind eye to the so-called 'torture flights'.

One EU inquiry has already accused ministers of putting up a wall of silence over 170 alleged stopovers by CIA-operated aircraft in the UK.

There have been repeated questions about British complicity with the policy of so-called 'extraordinary rendition', which involves sending terror suspects for interrogation in countries that carry out torture.

The move towards a police inquiry came in Scotland where Justice Secretary Kenny MacAskill said last night he was passing a dossier detailing more than a hundred flights to Scotland's most senior law official.

Campaign groups Amnesty International, Liberty and Reprieve, told Mr MacAskill they had evidence of 'systematic deception and cover- up'. An official EU inquiry, headed by Liberal Democrat peer Baroness Ludford, also identified cause for 'serious concern'.

Mr MacAskill said that while civil aviation was a matter controlled at Westminster, attempts to commit torture were crimes under Scots law.

The campaigners claim planes allegedly used by America's CIA were refuelled in Scotland on more than 100 occasions and that six named individuals were transported to another country for 'torture'.

They include Khaled Sheikh Mohammed, who has allegedly confessed to planning the 9/11 attacks.

Lord Foulkes yesterday angrily denied the accusations. He said the Intelligence and Security committee at Westminster had already held an inquiry which concluded there was no evidence to support claims that UK airports were used for extraordinary-rendition flights.