When a key section of the nation’s annual health report turns out to be a four-page economic forecast based on a hypothetical piece of legislation, alarms should sound. For Sir Liam Donaldson, the Chief Medical Officer, has set himself the goal of measuring the putative economic advantages of a ban on smoking in the workplace and public places, and in doing so has overreached himself.

Sir Liam claims on the basis of research he commissioned from the less-than-disinterested Department of Health that such a ban would be worth up to £2.7 billion to society at large. The question he hopes this figure will prompt is why the ban, which he has been recommending since last year, is not already in force. Yet a more important question is why someone in his unique position should have departed from his brief of offering solid counsel on medicine and public health to engage in cost-benefit analysis of interest chiefly to the hospitality industry. The answer comes in two parts: The ethical case for such a ban rests on the risks of second-hand, or passive, smoking; and those risks are simply not proven to the point that would warrant the ban.

There is no question that Britons would be healthier if none of them smoked. Smo-king remains the country’s single gravest public health problem, and highlighting its dangers is an obvious duty for any chief medical officer. Sir Liam has rightly done so, and for similar reasons he was right last year to give warning of a looming crisis of childhood obesity, and to single out a growing reliance on junk food as one of its causes. Yet just as junk food could not reasonably be banned in a democracy unless it harmed even those who smelt it, so legal restrictions on smoking are warranted only insofar as they protect non-smokers from real dangers posed by smokers.

The ills of passive smoking are not imaginary. Relatively reliable research suggests that living with a heavy smoker increases the risks of developing lung cancer by 20 per cent, and the children of smokers are far more likely than those of non-smokers to be admitted to hospital for asthma and other respiratory disorders. The evidence for a supposed link between smoking- related illness and exposure to other people’s smoke in bars and restaurants, how- ever, is much weaker than generally supposed, and it is in bars and restaurants, not private homes, that Sir Liam is calling for a ban. Such a step would be as fundamentally illiberal as a ban on alcohol because of the dangers of drink-driving. To bolster his position, Sir Liam cites data from the US indicating that smoking bans can benefit the restaurant trade instead of driving diners away, as some had feared. This approach ignores the ethical issues at stake and hardly constitutes a sound macroeconomic argument for a ban in this country. Such a measure would save £1.6 billion in healthcare costs by helping an extra 4 per cent of smokers to give up, yesterday’s report states. Perhaps. But taken to its illogical conclusion the eco- nomic argument would have to account for revenues lost to tobacco firms and a healthcare industry deprived of tens of thousands of long-term patients.

To have left himself vulnerable to such arguments, contrived as they may sound, shows how seriously Sir Liam has confused his role as adviser with that of advocate. He is aware of the history of his post, which was established in the mid-19th century with precisely these two roles. Yet the world has changed since then. Specifically, the BSE and other recent public health fiascos have given impartial public health advice even more of a premium. He should leave advo-cacy — and economics — to others.