Demands for a ban on smoking in UK parks and outdoor spaces have split the anti-tobacco lobby, with leading figures engaged in an increasingly bad-tempered war of words on the issue.
Lord Ara Darzi and Oliver Keown from the Institute of Global Health Innovation used an article in the British Medical Journal to argue that banning smoking in certain public areas would discourage children from taking up the habit.
"Crucially, it is an opportunity to support our population - young and old - to make healthier lifestyle choices easier.
"By reducing the geographical footprint where smoking is sanctioned and by limiting exposure to the practice itself, we can redress the observed norms against which park users and young people compare their personal smoking habits.
"Expanding smoking prohibition to broader public spaces will undoubtedly have a positive effect on our population's health."
But the comments won a stern rebuke from Simon Chapman, a leading tobacco control activist who led the charge for plain-packs in Australia.
Writing in the same magazine, Chapman said the proposal was scientifically illiterate and a breach of basic freedoms.
He argued that no studies had been done on exposure to smoke in parks or beaches "almost certainly because researchers with any knowledge of airborne exposures would appreciate that such exposures would be so small, dissipated, and transitory as to be of no concern".
The academic called on anti-smoking campaigners not to dress up their demands for a ban "in the language of public health" and said the logic of protecting children from the sight of smoking "is pernicious and… redolent of totalitarian regimes in their penchants for repressing various liberties, communication, and cultural expression not sanctioned by the state".
"Political support for dissuasive, but not coercive, policies such as plain packaging and high tobacco tax rates has been bipartisan, from the left and right of politics. This would almost certainly not have happened if we had abandoned the ethical concerns that some are demanding."
Earlier this month, two city squares in Bristol were the first open-air public spaces to go smoke-free, albeit on a voluntary basis
Lord Darzi released a report last year demanding smoking be banned in all London's parks and around its landmarks, such as Parliament Square and Trafalgar Square. If implemented, the policy would have meant 40% of London went smoke-free.
But eyebrows were raised when Lord Darzi refused to debate critics on the measure and only agreed to interviews which did not include an opponent of the plan.
Simon Clark, director of smokers'-rights group Forest, said:
"There's nothing to suggest that lighting up in the open air is harmful to anyone other than the smoker.
"Campaigners say a ban will discourage children from smoking but there's no evidence that the sight of a stranger smoking encourages children to start. The principal reasons are peer pressure and the influence of family members.
"We must be careful we don't create a world only puritans can inhabit."
Cities including New York, Toronto and Hong Kong have already banned smoking in key outdoor locations.