Parliament's security advisers have abandoned the idea of using fingerprint technology to enhance the security surrounding the Commons and the Lords for fear it could pose a risk of mutilation of MPs, Peers or staff.

The authorities' fear is that potential suicide bombers would have no compunction cutting of politicians' fingers in an attempt to defeat a system which relied on automatic readers to verify passholders' identities.

Experts also feared that existing fingerprint technology is unreliable and cannot cope with dirty or sweaty fingers, or those with particular racial characteristics.

The decision was taken following a review of the security of the Palace of Westminster, including the construction of massive steel barriers to prevent the approach of suspect vehicles and the use of x-ray and other machines to scan visitors.

One aim is to reduce the cost of physically monitoring the thousands of politicians, aides and staff who use the precincts every day.

The risks range from personal assault with a weapon - one Prime Minister was shot in a corridor approaching the Commons - to the nightmare of a chemical or biological attack, to purely embarrassing disruption of a debate.

The choice of the new system is, of course, secret.