Dame Stella Rimington, the former director general of MI5, has waded into the debate about ID cards, warning that they will be "absolutely useless" unless they can be made incapable of being forged.
Speaking at the annual Association of Colleges conference in Birmingham, Dame Stella said: "ID cards have possibly some purpose but I do not think that anybody in the intelligence services, particularly in my former service, would be pressing for ID cards.
"They may be of some use but only if they can be made 'unforgeable', and all our other documentation is quite easy to forge.
"If we have ID cards at vast expense and people can go into a back room and forge them they are going to be absolutely useless.
"ID cards may be helpful in all kinds of things but I do not think they are necessarily going to make us any safer."
Dame Stella's remarks come just after the government suffered a defeat in the House of Lords on its controversial ID card legislation.
Michael Parker, a spokesman for the NO2ID campaign against identity cards, welcomed the opinion of someone so senior and knowledgeable as Dame Stella, and hoped that her comments would persuade the government to reconsider its plans.
Shadow Home Secretary David Davis has referred to the ID card plan as Labour's "plastic poll tax".
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