HOWARD STOATE MP is happy that Mr Blair has allowed him a free vote to ban smoking in all public places in England. For the Honourable Member is also a GP, and he claims that he “could not have voted, as a doctor, for a partial ban”.

Why not? Why should a doctor be any more inclined than other MPs to vote for a total ban on smoking? There can be no doubt that doctors are so inclined, not just individually but collectively. The British Medical Association is always calling for unhealthy substances, such as tobacco and fattening foods, to be banned, regulated or taxed. And they do not restrict their regulatory requests to comestibles. In 2000 they called for the regulation of Calista Flockhart on the ground that watching her on TV causes anorexia nervosa.

But why are doctors such unusually enthusiastic prohibitionists? They possess no special knowledge lacked by the rest of us. Everybody knows that smoking increases the chances of heart and lung disease. Why should a doctor MP be keener to ban smoking than a lawyer MP, a banker MP or a gentleman MP?

I suspect their profession inclines them to overestimate the importance of health. They think that when it comes to a trade-off between health and anything else — be it pleasure, wealth or liberty — health should always win. Doctors confound what is good for us with what is good for our health.

Workplace safety regulations, such as this ban on smoking (it is supposed to benefit bar staff), are a perfect example of how this confusion leads legislators astray. Consider coalmining, a job even more dangerous than working in a smoky bar. Would measures to make coal mining safer benefit coal miners? Dr Stoate and his friends at the BMA will probably think so. But they are wrong. Making coal mining safer would only injure coal miners.

When a job is dangerous, fewer people are willing to do it. The more dangerous it is, the smaller the supply of willing labour and, hence, the higher the pay. A dangerous job, such as coal mining or working on an oil rig, is one of the few legitimate ways an uneducated man can earn high wages.

“Danger money” is not just a joke expression. It is a real consequence of supply and demand in a free labour market. And it explains why you cannot help coalminers (or any other workers) by making their jobs safer.

Anything that successfully did so would increase the supply of willing coalminers and so lower the pay. What miners gained in safety, they would lose in money. In the end, they would be no better off.

In fact, they would be worse off. Those who are now coalminers are people for whom the danger of mining is more than compensated for by the pay. Otherwise, they would not be miners. Change the job so that it is safer but pays less, and the deal does not suit them as well. Now it suits many non-miners better. Those who did not like the previous trade-off between the danger and the money might now apply for a job down the pit.

Politicians always claim that their safety regulations are motivated by concern for people doing dangerous jobs. Yet the beneficiaries are always people who do not do dangerous jobs. Workplace health and safety measures are a zero-sum game in which wealth is transferred from the brave to the timid.

As with coalminers, so with bar staff. A ban on smoking will lower their wages, since more people will be willing to work in this newly healthy job. Those who do not mind the smoke but like the higher wages — that is to say, current bar staff — will be the losers.

Still, you might think there is no loss in the policy. As I said, it is a zero-sum game. Transferring wealth from current bar staff to potential bar staff seems pointless, but futility is a small defect by the standards of public policy in Britain.

Alas, the policy is worse than futile. It may have no net effect on the welfare of employees, but it harms their employers. Employers benefit from improving workplace safety when it reduces their wage bill by more than it costs. Publicans do not voluntarily ban smoking because they figure the revenue lost from smoking customers would exceed the wage savings. They do not ban male beer-drinkers, who present their staff with some risk of violence, for the same reason. And similar thinking explains why the windows in most offices are not made of bullet-proof glass.

Left to his own devices, a profit- seeking employer would get workplace safety exactly right, taking just those measures that save more than they cost. But our legislators do not have it in them to leave anyone to his own devices. Employers must be forced to make their workplaces safer than they would choose to, imposing a cost on them that is offset by no benefit to their staff.

Such policies can look like a good idea only to people suffering from a health fixation. If Howard Stoate is right that “as a doctor” he cannot help himself, then perhaps we need to consider another prohibition: a total ban on doctors in parliament.

Jamie Whyte is the author of Bad Thoughts: A Guide to Clear Thinking

Times Recommends

• Brown is in denial. Cuts are expected
• Fight our genetic urges? Slim chance
• Beware: dogs in mangers. Barking