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Authorities can gain further personal information stored on the chip to confirm the holder's identity. This validation process can be done anywhere - on the streets, in airports, schools, banks, swimming pools or office buildings.
You will not hear any government emphasising these aspects. Instead, the new ID systems are benignly promoted as "citizen cards" that guarantee entitlement to benefits and services.
Five years ago, the Government quietly buried proposals for ID cards when it discovered that they would cost billions of pounds more than expected, would do little to prevent crime, and might become wildly unpopular.
How much more unpopular will they be when people learn that a scan of their body parts will be required?
If an ID card was unworkable five years ago, why would it work now? The short answer is that it would not - unless the biometric were added and the whole system verified through a national database. That is not a card: it is a national surveillance infrastructure.
If such a scheme is introduced in the current climate, three outcomes are inevitable. First, a high-security card will become an internal passport, demanded in limitless situations. (Don't leave home without it.)
Second, millions of people will be severely inconvenienced each year through lost, stolen or damaged cards, or through failure of computer systems or the biometric reading machinery.
Finally, the cards will inevitably be abused by officials who will use them as a mechanism for prejudice, discrimination or harassment.
No one has been able to identify any country where cards have deterred terrorists. To achieve this, a government would require measures unthinkable in a free society.
The Government thus faces a choice. Either it introduces a high-security biometric card that will challenge every tenet of freedom, or it introduces a low-security card that will soon be available to criminals and terrorists on the black market.
Or, of course, it can scrap the whole idea and concentrate on more proven measures to deal with terrorism.
Simon Davies is visiting fellow in the department of information systems at the London School of Economics and director of the watchdog group Privacy International