opinion: YORKSHIRE TERRIER: 'When the light bulb goes in a GP's surgery, they do not need to fill out a form in triplicate for the works department. The doctor simply stops at a shop on his rounds'

'The law of unintended consequences' is an expression coined by the writer and historian Sir Karl Popper. Popper's Law, and Robert Burns' rather better known lines on mice and men, might have been written especially with the NHS in mind - not least the government's spanking new service, NHS Direct.

Costs per call are alarmingly high, although in fairness fixed start- up costs have had to be included in the calculation. But causing much more head-shaking is the discovery that far from reducing demand on GPs, their workloads may actually be increasing.

According to a recent study, before ringing NHS Direct 17 per cent of callers would have made an appointment to see their GP; afterwards, 20 per cent did so.

But then the road to hell has always been paved with good intentions, and the NHS perpetually encounters well-meaning folk who fail to think through the consequences of their actions.

One authority some years ago committed itself to employing a GP for homeless people without assessing the relative merits of alternative provision or even whether it had sufficient homeless people to justify such expenditure.

It took three years and many thousands of pounds of public money before the ridiculous truth emerged - almost no homeless people lived in the area.

The falsest assumption of all can be traced to the 1940s - the naive belief that the cost of the proposed NHS would decline as the population became healthier. That illusion lasted less than 12 months.

One key marker was the number of free NHS prescriptions dispensed - Aneurin Bevan had confidently predicted 140 million annually - the actual number was more than 200 million.

Bevan and his young protege, Harold Wilson, resigned from the Cabinet in protest at the inevitable introduction of prescription charges.

Wilson was a slow learner: in 1965 his new government abolished prescription charges - only to see numbers immediately rise by 16 per cent. Soon after, they had to be reintroduced.

Not that lack of foresight is restricted to managers and politicians.

By the early 1950s, 2,500 premature babies a year were being blinded by being given oxygen shortly after birth. The cause and effect relationship was discovered only in 1954.

Naturally, as a matter of good clinical practice, the amount of oxygen given to premature babies was reduced.

It took almost another 20 years before another study pointed out what should have been predicted - that for every baby saved from blindness, 16 were now dying from lack of oxygen.

Some dogma-inspired acts of folly are worse than others: the pursuit of a salaried GP service is a major one

The idea has been around for a long time. The topic was under discussion in 1910 when Lloyd George's draft National Health Insurance Act was the subject of negotiation between the government and the medical profession.

A salaried pilot project was run in Birmingham in 1917. The issue was mooted again in the Dawson report of 1920, and was being actively promoted by the Socialist Medical Society in the 1930s.

By 1934, the Labour Party had formally adopted a salaried GP service as official policy.

The first white paper on the NHS published in 1944 claimed a strong case existed for a salaried service, but by 1945, in the face of the profession's intense opposition, the government backed down.

GPs' fears were not finally calmed until Bevan himself confirmed to Parliament in April 1948 that a salaried service could never be introduced by ministerial regulation alone.

But the idea refused to die. Kenneth Robinson, Labour's health minister in 1965, was a keen supporter of the salaried option. Matters might have progressed further had the Family Doctors' Charter and the threatened resignation of 20,000 GPs from the NHS provided Mr Robinson with better things to do with his time.

And so to the present day and Primary Care Act pilot schemes, under which salaried GP services may be established.

This really is unwise: the NHS's greatest asset is a GP service provided by self-employed independent contractors. By a massive margin, the greatest proportion of work done in the NHS occurs in general practice - and it is done with considerable economic efficiency.

The reason for that is blindingly obvious: GP practices are small organisations and avoid all the diseconomies of scale found elsewhere in the NHS.

General practice costs trivial amounts to support. When the light bulb goes in a GP's surgery, they do not need to fill out a form in triplicate for the works department. The doctor can simply stop at the corner shop on his rounds and buy one.

If a GP is ill, they do not ring in to report sick and leave the problem to someone else - they arrange a locum personally.

A salaried service would inevitably require a whole new tier of bureaucracy to run the system - and does anyone really want that?

Fortunately, most of the 30,000 GPs have had more sense than to be tempted by the imagined advantages of entering a managed system - currently only 65 GPs are working in pilot schemes.

These schemes will eventually fail - but we might as well do what we can to help ensure the thin end of this thoroughly undesirable wedge is quietly returned to the history books sooner rather than later.

Steve Ainsworth is a former primary care manager.