Both the Lib Dems and the Conservatives have said they would scrap ID cards, and this is good news. What is equally important, however, is the way in which ID cards are used. Citizens in some countries with national ID cards (such as France or Spain) rarely show them on a day-to-day basis. Paradoxically, we don't yet have cards, but we do have a culture of routine ID checking. "Do you have any ID?" is a question we increasingly face when going about our business in the streets or at work.

A Manifesto Club survey found that people in their late 20s and 30s are being routinely checked not just for buying alcohol, but also for attempting to purchase items such as barbecue skewers, bleach, paracetamol, UHU glue, matches, cigarette papers, even a "gentleman's manicure set". Two women in their late 20s had been ID-checked for bottles of wine so frequently that they now carry their passports to go to the supermarket.

Passport checks are becoming routine in working life too. Some organisations have started collecting passport details from staff of 10 or 20 years standing to check they have the right to work in the UK. Universities including Nottingham, Southampton, Lancaster and Lampeter have asked visiting lecturers and external examiners to produce their passports before they can be paid. The musician DJ Moth reports that one of London's major jazz clubs in Hackney now requires performers to give passport details.

Then there is the downright bizarre. A reader of the magazine Today's Railways Europe wrote in to say that he was asked to produce his passport in the Luton branch of Thomas Cook, when attempting to buy a copy of Cook's European rail timetable. He was told that this was for "security reasons".

As a point of historical comparison, the Common Travel Area] has allowed passport-free travel between the Republic of Ireland and the UK since 1923, including throughout the Troubles. Now the Home Office is attempting scrap this agreement and oblige people to show ID documents or be refused passage. Regular travellers on ferries between northern Ireland and Scotland already report that passengers (usually of African origin) are now being pulled out of the queue and asked to show their documents.

Shops and businesses ask for ID under the threat of heavy fines for serving underage drinkers or for employing somebody who is not entitled to work in the UK. Yet like the ID card scheme itself, this is a policy looking for a justification. At base, this is less about combating specific social issues than about the growing state regulation of citizens.

The meaning of ID checks is that we are constantly being asked to (as the posters say) "Prove it!": to prove our age or nationality, to prove that we are allowed to be where we are, doing what we are doing. The assumption is that unless we can produce documents we are probably not supposed to be here, not supposed to be giving a lecture or buying barbecue skewers.

This culture of checking calls forth ID cards of some kind (unless we just start carrying our passports around everywhere). Companies have sensed a business opportunity and produce proof-of-age cards under the banner of the officially accredited Pass Scheme, "the national proof-of-age accreditation scheme". One of these cards has the horribly revealing name, Validate UK: "a voluntary proof of age scheme for all ages".

The illiberal underpinnings of these schemes are clear. To be a UK citizen you must be validated. "No pass, no sale", says the banner on the Pass Scheme website. And so the demand of "Pass, please!", so beloved of authoritarian regimes, comes to the British Isles. You do not have a right to pass: you need to prove your legitimacy by proffering your documents. No pass, no sale; no pass, no job; no pass, no ferry crossing to Holyhead.

Challenging this culture of ID checking is as crucial as taking on the ID card scheme itself. As free citizens we should not have to produce our papers at the local supermarket. We must assert again our right to pass.