Whenever a particular idea appears to have captured the centre ground of politics it is time to look at it with a beady eye. This applies now to what is sometimes called the "choice agenda". The idea is that core welfare state services, above all health and education, should remain state financed, but that the users should have a greater choice, for instance, among schools and hospitals. At a minimum they should be able to select among state providers; but in the more daring version, private enterprise providers would be able to compete too, as long as the services remained free at the point of entry.

Labour politicians who call themselves Blairite have made this programme their flagship and suspect Gordon Brown, the prime minister, of not being sufficiently keen on it. The same set of notions is just as popular among the self-styled progressive wing of the Conservative party, whose members could hardly wait for Tony Blair to retire so that they could claim the programme as their own.

Although sometimes better than nothing, the type of choice envisaged is extremely limited as long as no top-up payments by patients or parents are allowed. Money should not become a fetish, but is nevertheless an extremely useful human invention and a main instrument by which choice can be exercised. To forbid some people from paying more to obtain a different quality of service is a sign of a belief not in equality but in uniformity. It is apparently acceptable for a citizen to lay out cash for a holiday in Las Vegas but not for a private room in a National Health Service hospital.

The whole discussion reminds me of the £50 travel allowance that Harold Wilson's Labour government imposed in the 1960s as part of a forlorn attempt to stave off devaluation of sterling. This could be seen as an example of the "choice agenda". UK residents could travel anywhere they liked, from China to Peru, as long as they did not take more than £50 per head out of the country. True choice would, of course, have involved the freedom to decide how much to spend as well as where to go.

The search for a third way between "free" state services and private payment has its roots in one rather unattractive aspect of the electorate, especially its middle-class members. They are too mean to pay themselves for public services, but they also begrudge paying taxes for state provision. So they are thought to be in the market for any device that disguises the alternatives.

Of course, the NHS is not entirely free at the point of delivery. Aneurin Bevan, minister of health in the postwar Labour government, resigned when Hugh Gaitskell, then chancellor, insisted on charges for teeth and spectacles. But the dogma of avoiding charges continues.

Those who can see through the so-called choice agenda do not have to agree on alternatives, of which there are many. At a minimum, the state could provide and charge for extra services, such as extra comforts for hospital patients or lessons in playing musical instruments. One step further would be to allow private providers to offer such extras on a competitive basis. A more daring step would be to allow the private sector to provide mainline health or educational services for a fee, but with some input of state finance. Beyond that there are really radical options, such as tax rebates for those who go completely private and thus allow the government to reduce its expenditure.

There is no need to be starry-eyed about any of these options. Medical insurance is no magic wand to allow the citizen to use private medical services, as those of us who have taken this route soon discover. It is quite normal to exclude from insurance cover any malady from which the patient has already suffered. The US presidential candidate Barack Obama is toying with the idea of making such exclusions illegal. But if we go too far along this route the insurance companies become simply state agents and what the Americans call "socialised medicine" has entered by the back door. In the UK the insurance companies have agreed for a temporary period not to ask for DNA data. But for how long can this agreement last, if and when DNA records come to provide detailed health prognoses? Insurance is well suited to covering events that are unpredictable at the individual level and premiums have to be based on statistical averages. It is not nearly so well suited for assessable risks.

But I risk wandering too far from my self-imposed, purely negative task of uncovering the impoverished nature of the bipartisan espousal of so-called choice. In fact, the present path is not always better than nothing. Parents who do not like local authority schools are being encouraged to opt for faith schools or for academies supported by wealthy citizens, some of whom have strong religious or other beliefs. Such schools then have a cost advantage they would not have if parents had cash or vouchers that they could spend on a school that they really preferred.

My main point, however, is not to argue for an early root-and-branch reform of the welfare state. It is to say how very sad it would be if the next election were fought between rival but similar versions of a very limited extension of client choice.

*references to journals etc. Can do hyperlinks on these if there's a web address

www.samuelbrittan.co.uk