Mr Aitken, 55, voluntarily attended a central London police station and was later released on police bail without charge, pending further inquiries into the collapse of his libel case against the Guardian and Granada Television last year.

Scotland Yard's Organised Crime Group began its investigation after the editor of the Guardian, Alan Rusbridger, wrote to the Metropolitan Police Commissioner, Sir Paul Condon, calling for Mr Aitken to be prosecuted for perjury.

The allegations centre on his libel action last June, when Mr Aitken gave evidence under oath. At the heart of the case, which collapsed after 12 days, was a dispute over who paid the bill for Mr Aitken's stay at the Paris Ritz in September 1993.

The results of Scotland Yard's nine-month investigation will be considered by the Crown Prosecution Service before any decision over charges is taken.

Conspiracy to pervert the course of justice carries a maximum life sentence. Mr Aitken lost his Thanet South seat at the general election and resigned from the Privy Council.