I used to take the view - admittedly without giving the arguments much serious thought - that the introduction of ID cards was probably harmless.

I accepted the oft-repeated mantra that if you have nothing to hide, you have nothing to fear.

And if IDs would be a useful tool in helping the police deal with crime, they were probably a good thing.

I could not have been more wrong.

The threat to introduce IDs is now serious.

The implications for all of us are dangerously intrusive and almost certainly permanent.

Given the present crisis, the most important question to ask is: Will the introduction of IDs help to catch terrorists? The straight answer is no.

There is no evidence from anywhere this would be the case. None of those advocating the introduction of IDs have yet explained how such cards might have prevented the attacks on New York and Washington.

Yet all the terrorists involved almost certainly carried some kind of ID.

In 1995, Michael Howard, then the Conservative government's home secretary, issued a Green Paper setting out the options about IDs.

In the end of course, he decided against proceeding.

The Commons home affairs select committee concluded there was no firm evidence ID cards had reduced crime in any countries that used them.

The cards would not even stop the arrival of asylum seekers.

And there is a mass of well-documented evidence to show unscrupulous employers here ignore National Insurance checks and minimum wages when using illegal immigrants for temporary work. They would not ask for IDs either.

The alarming thing about 21st Century ID cards is no government, especially one as manipulative, interfering and authoritarian as New Labour, could resist using the latest smartcard, micro-chip technology.

As well as your photograph, name, address and birthday, masses of other information could be included. The chip could store your credit worthiness, tax and marital status, criminal record, health record and much more. And such cards are not wholly secure, not all that difficult to forge.

More complex cards can include biometrics - unique, human characteristics such as fingerprints and iris scans used for automatic identification.

This is not an argument against reassessing Britain's anti-terrorist legislation.

But David Blunkett's new-found enthusiasm for ID cards makes little sense and such things are not a substitute for genuine anti-terrorist measures.

If the Home Secretary has his way and reintroduces IDs, they will undoubtedly become a permanent feature of our lives.

No bureaucracy with easy access to so much personal and private information about us all would be prepared to give up such enormous power. And knowledge is power.

We have a right to privacy, to live our lives anonymously if we so wish. We do not have to be subjected to the prying eyes of the State and the police so that David Blunkett can make a bold gesture simply to appease the moment. Which is all the IDs would achieve.