Labour has pledged to re-introduce ID card plans

The Home Office has admitted that the move is being considered, but stressed no decision had yet been taken.

Doug Jewell, of human rights group Liberty, believes such a system could lay the foundations for ID cards.

He said: "We have a certain fear that when Parliament is deciding on ID cards the government will say, 'Look, the infrastructure is already in place'."

Labour has pledged to re-introduce its ID card plans if re-elected on 5 May.

No final decision has yet been made on the inclusion of a second biometric such as fingerprints or irises in passports Home Office spokesman

But the Home Office said fingerprinting could be introduced without new laws because passports are issued by Royal Prerogative.

Mr Jewell, campaigns co-ordinator for Liberty, said he had no problem with fingerprints and other information being used for passports.

But he said the 70 fingerprinting centres and database storing applicants' details that are expected to be needed could be easily used later to process ID cards.

Digitised photograph

Fingerprinting is among a number of changes being considered for passports.

By the end of 2006, there will be face-to-face interviews for the 600,000 new applicants who come forward each year.

This will have been preceded in 2005 by the introduction of a digitised photograph with a face-recognition microchip inside.

A Home Office spokesman said: "No final decision has yet been made on the inclusion of a second biometric such as fingerprints or irises in passports."

Labour proposes an ID card scheme costing an estimated �3bn although one academic study has found that costs may be much higher.