Smoking bans in public places lead to children being exposed to higher levels of tobacco smoke at home, a study by University College London shows.
Designated smoking areas were favoured
Experts found that smokers were more likely to light up at home if prevented from doing so in cafes and bars.
The researchers favoured designated smoking areas over an outright ban, which they claim displaces the problem.
Data from almost 30,000 non-smokers across the US, in states with different anti-tobacco policies, was examined.
The study comes ahead of a meeting of the Commons Health Select Committee on Monday which is expected to criticise the government for failing to follow the Scottish Executive's lead.
Smoking will be banned in public places in Scotland from 26 March next year.
There is currently no specific timescale for the introduction of a complete ban in England.
Dr Jerome Adda, of the University College London's department of economics, said their research showed outright bans may not be the best solution.
"Policies aimed at reducing exposure to tobacco instead induce changes in behaviour that can offset these policies.
"Bans in bars may induce smokers to spend more time at home, and therefore expose other members of the household, especially children."
Rod Bullough, of the pro-smoking lobby group Freedom2Choose, said: "This proves what we've said to the Scottish Executive all along. They have their own agenda and their blanket smoking ban is just window dressing."