WHEN, ON the Radio 4 Today programme, David Hockney squared up to Julie Morgan, a Labour MP, he proved an invigorating denouncer of the nanny state. Against Ms Morgan’s arguments for a ban on smoking in public places, Hockney fulminated: “I think you are too bossy, chum. You are dreary.”

New Labour’s least appealing characteristic is its puritanism. Even where it expands private choice — lowering the age of consent for homosexuals — its arguments are exhortatory rather than libertarian. More usually, as on foxhunting, the Government’s instincts are to ban rather than regulate, and to regulate rather than allow people to arrive at private agreements.

Yet in this case the sanctimonious MP merits support. The bluff artist lambasting the Bossy Tendency is wrong. A smoking ban in public places is workable, as the Irish precedent shows, and principled.

Hockney speaks for the smokers’ rights group, Forest. For the group’s chairman, Lord Harris of High Cross, choice on tobacco is a lineal descendant of the “dogged persistence of economic liberals in a century-long struggle against often well-meaning collectivists in all parties”. Yet liberals recognise the problem of what economists call “externalities”: costs or benefits that accrue to someone other than the person responsible for creating them.

Pollution is an externality. Liberals often argue that property rights are a better way of coping with it than regulation. If a factory pollutes an adjoining river, then its owner will have a greater incentive to conserve resources if he has to compensate someone with a property claim to that stretch of river.

If Forest were arguing a consistent libertarian case, it would come up with a comparable scheme for compensating those who suffer from pollution caused by cigarette smoke. Forest has not done that, because it cannot. Private property rights are no solution, because it is impossibly complex to identify all who suffer the inconvenience and discomfort of a smoky atmosphere, and to draw up contracts with them to buy the right to pollute the air.

The right to pollute is not an axiom of a free society like the right to speak, worship or associate. It is the claim of a lobby group portentously appropriating high principle for self-interested ends. To adapt G. K. Chesterton’s advice to another public worthy: chuck it, Hockney.