Smoking bans in pubs, clubs and restaurants increase the exposure of children to tobacco fumes, according to new research by independent analysts.
According to a study reported in the Scotsman newspaper, stopping smokers from lighting up in places of leisure forces them to smoke more than they previously did at home.
Therefore an unwanted consequence is increased exposure faced by children and non-smokers.
We find that bans in recreational public places can perversely increase tobacco exposure of non-smokers by displacing smokers to private places where they contaminate non-smokersStudy by researchers at UCL.
The researchers studied data from the US, where bans have been in place for a number of years.
The presence of the nicotine by-product cotinine was recorded.
The results found that bans on buses and in places like shopping centres reduced the levels of tobacco inhaled by non-smokers.
But once bans were imposed in recreational places such as pubs, the results changed.
The researchers said: "We find that bans in recreational public places can perversely increase tobacco exposure of non-smokers by displacing smokers to private places where they contaminate non-smokers."
They concluded: "Governments in many countries are under pressure to limit passive smoking.
"Some pressure groups can be very vocal about these issues and suggest bold and radical reform. Often, their point of view is laudable but too simplistic in the sense that they do not take into account how public policies can generate perverse incentives and effects."
The research was carried out by two economics academics from University College London, Jerome Adda and Francesca Cornaglia.
Neil Rafferty, Scottish spokesman for the smokers' rights group Forest, told the paper: "MSPs were warned that a comprehensive smoking ban would mean greater exposure for children but, typically, they ignored this and instead forced through a law which not only exposes children to tobacco but robs adults of their personal freedom."
However, Maureen Moore, chief executive of ASH Scotland, poured doubts over the quality of the research.
She said: "Tobacco industry front groups frequently claim that banning smoking in public places will lead to increased exposure of children in the home. All published international research goes against these claims."