The research, carried out in Britain, Ireland, France, Germany and the Netherlands, found that a significant proportion of smokers also decided to ban smoking in their own homes after national public smoke-free laws were introduced.

Some opponents of workplace or public smoking bans have argued that smoke-free laws might lead to a displacement of the habit into smokers' homes, possibly increasing the exposure of non-smokers, particularly children, to second hand smoke.

But Ute Mons of the German Cancer Research Center and the Unit of Cancer Prevention at the World Health Organization (WHO) Collaborating Center for Tobacco Control in Heidelberg, whose work was published in the journal Tobacco Control, said her findings suggested just the opposite.

"On the contrary, our findings demonstrate that smoke-free legislation may stimulate smokers to establish total smoking bans in their homes," she wrote in the study.

Smoking is known to cause lung cancer, which is often fatal, and other chronic respiratory diseases. It is also a major risk factor for cardiovascular diseases, the world's number one killers.

The WHO warned last year that tobacco would kill nearly 6 million people in 2011 including 600,000 non-smokers exposed to second-hand smoke. It fears the annual tobacco death toll will rise to 8 million by 2030.

Tuesday's research was based on two surveys conducted in 2003/4 and 2008/9 and involved more than 4,600 smokers in the four countries with smoke-free legislation, as well as 1,080 smokers in Britain which served as comparison country at a time when it had no public smoke-free laws.

Before bans came into force, most smokers had at least partial restrictions on smoking at home, although the proportions varied significantly among all four countries, with the highest levels of restrictions in Germany and France, the researchers found.

But after smoke-free legislation was enacted, the percentage of smokers who banned smoking at home rose by 25 percent in Ireland, 17 percent in France, 38 percent in Germany and 28 percent in the Netherlands, the study showed.

Home smoking bans were more likely to be adopted when the smoker planned to quit the habit, when there was a birth of a child, and when the smoker was someone who had voiced support for a smoking ban in bars.

In raw data terms, the percentage of smokers in Britain who put in place home smoking bans also rose 22 percent between the two surveys, the second of which was carried out just a few months before a smoking ban came into force in the UK.

But after taking account of confounding factors such as demographics and smoking history, the researchers found the percentage of smokers banning smoking at home had increased significantly in France, Germany, the Netherlands and Ireland, but had not significantly increased in the UK.

(Editing by Paul Casciato)

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