"Are your papers in order sir?" When you hear these words in an old film, you know that the hero is about to see the nasty side of a police state. For us, the identity card is associated with the spy at the next restaurant table and the smiling guide from the Ministry of Internal Security. If certain people have their way, this will change within the lifetime of the present Parliament.

Apart from the Irish Republic, Ours is the only country in Western Europe not to have an official identity card scheme. We are almost unique in the developed world in that we cannot be stopped at will and made to show proof of identity. It may be advisable for any number of reasons to carry identification. But there is as yet no law compelling us to do so.

The advocates of change normally portray this uniqueness as a curious anomaly, without the slightest justification. We live in a dangerous world, we are told. The authorities are powerless before the forces of lawlessness and disorder. The clearing banks lose £100 million every year in fraud. Food companies are blackmailed into paying thousands into untraceable building society accounts. The Cabinet itself cannot meet in safety from the assaults of Irish terrorists. If only we all had identity cards that the Police could look at on demand, the argument ends, crime and terrorism would be so very much easier to fight. As for privacy - why, "those with nothing to hide have nothing to fear".

The plain fact, of course, is that crime and terrorism would not in the least be diminished. They might drop for a few months while adjusting, then would carry on much as before. Identity cards would be no harder to forge or falsify than passports or credit cards now are. Most illegal occupations would face a certain rise in costs. Counterfeiting would expand. That is all.

That is what happened in the European countries long ago. The French are no more law-abiding than we are. If we exclude Northern Ireland, they are certainly more threatened by terrorists than we are. That is what happened in Hong Kong at the beginning of the last decade. There, very sophisticated identity cards were issued to stem the flow of immigrants from China. The scheme was a failure. The local printing industry was turning out perfect copies within a week. Believing the same would not happen here requires either great ignorance or great stupidity.

Now, those in favour of identity cards may well be both stupid and ignorant. But, to give credit where due, they are not in themselves monsters. They are simply the defenders of what Margaret Thatcher has called "the Nanny State". These are not monsters. Nearly always, they have the very best intentions. Most of them want more regulation because they believe it would be good for us. Most of the rest are only concerned with how to increase their own status and salaries. But well-intentioned or not, they are now advocating a measure that has very disturbing implications.

The amount of personal information available to a Policeman in the street is growing all the time. It is obsolete to think in terms of his merely inspecting a card and checking the number off against a list of wanted malefactors. The humble bar code potentially makes available every record on each of us ever opened. There is no technological reason why a Police car should not be fitted with a radio link to some central computer, from which our names, addresses, likenesses, occupations, medical and criminal histories, and banking details could be extracted as required.

To be sure, this would not all be gathered together at once. We should need first to be broken into the idea of carrying official identification. But it would need only one railway crash for the tabloid press to start asking why blood groups and other relevant information were not included on the cards. The Police themselves would insist on access to criminal records. The full surveillance would come. It might come slowly. But it would come.

And here is the great danger. Identity cards confer on the State a huge but almost invisible means of social control. Their introduction here would strike a surer blow against non-conformity than any other law currently to be imagined.

It takes no gift of prophecy to guess that their first testing and refinement would be in the harrassing of unpopular minorities. There are few powers that our Police would more enjoy using than that of taking the names of people selling Militant on street corners, or of people coming out of gay bars or bookshops. Strange hair styles, CND badges, leather trousers, funny religious views - what better way to frighten many of their possessors back to conformity then letting them think themselves on some List of Deviants to be Watched?

We must never let go in this country of one very simple truth. To be stopped and questioned, on no probable cause, is to suffer an outrageous and humiliating loss of freedom. This is so whether or not we have anything to hide. So long as we obey the law, no one has any more right to demand our names and addresses than to film us sitting on a lavatory pan. To say otherwise is to concede to the State a still greater role of prying into - and ultimately of regulating - our lives.

The Victorians realised this. At the beginning of the 19th century, Jeremy Bentham had written eloquently on the benefits that would flow from having silhouettes made and centrally stored of everyone's profile. They would be hard to alter, and would reduce fraud and vagrancy. They would contribute so marvellously to "the greatest happiness of the greatest number" that no one but a fool could not agree with him. As an alternative, he toyed with the idea of tattooing a code number on every forehead in the country. For this, as for many other of his projects, he was regarded for the next hundred years as a sinister eccentric.

We put up with identity cards during the War. But many violations of rights were tolerated then for the sake of beating the Germans. With the coming of peace, the Government was forced to end the scheme. Too many people were tearing their cards up in public.

What will we do when, by whatever means, it becomes the law for us to carry identity cards? We shall resist them. At least, I hope we shall resist them. For, if we do otherwise, we shall at a stroke have lost much of our remaining freedom.