In order to protect children from second hand smoke a number of British doctors have called for smoking to be banned in cars and parks.
The ban called by the Royal College of Physicians (RCP), says that millions of children are exposed to second-hand smoke at home, which is a major hazard to their health, and reducing the level of exposure should be a priority.
Although adults occupy most cars, it would be impractical to apply the ban only to cars carrying children, the college said.
In a major new report on the impact of passive smoking on children, the RCP says it is time to capitalise on the gains achieved by the ban on smoking in enclosed public spaces, imposed in England in July 2007.
Experience from other countries shows extending the ban to a wide range of public spaces, including playgrounds and beaches, can be "popular and successful".
Passive smoking is responsible for a huge burden of disease on children, including one in five of all cot deaths, 200 cases of meningitis, 22,000 cases of asthma, and 120,000 middle-ear infections a year.
An estimated two million children are exposed to tobacco smoke at home.
A ban on smoking in cars is necessary because the confined space increases the level of exposure and the harm caused.
Smoking should also be banned in places such as parks, stricter penalties should be imposed on shops that sell cigarettes to children, and the price of tobacco should be increased, the report says.
The recommendations were welcomed by health organisations but attacked by the tobacco lobby.
The smokers' group Forest said the claim that the health of millions of children was at serious risk was a "gross exaggeration" and that changing people's behaviour should be achieved by "education and encouragement, not by legislation and enforcement".
"If you ban smoking in cars, which is a private space, it's a small step to banning smoking in the home," the Independent quoted Simon Clark, the director of Forest, as saying.
"Both measures are unacceptable and unenforceable. We wouldn't encourage people to smoke around children but adults should be allowed to use their common sense and act accordingly.
"These proposals go way beyond what is acceptable in a free society," he said.
It is almost 50 years since the RCP published its landmark report highlighting the dangers of smoking in 1962, which marked a watershed in attitudes to the habit.
Up to that point, it had grown steadily in popularity, with more than 80 per cent of men smoking.
From the 1960s onwards, smoking started its long decline - today, around 21 per cent of adults smoke.
However, two-thirds of smokers say they want to give up, nine out of 10 of them for health reasons and fewer than three out of 10 for cost reasons.
Smoking is more popular with younger adults - among 20- to 24-year-olds, 31 percent smoke.
Children growing up with parents or siblings who smoke, in addition to suffering harm to their health, are 90 per cent more likely to become smokers themselves.
The report estimates the cost to the NHS of treating children for conditions caused by passive smoking at 27.3million pounds a year.
Smoking is banned in cars carrying children in some states in the US, Australia and Canada. The most stringent legislation is in Mauritius, where smoking is banned in all private vehicles carrying passengers.
"This report isn't just about protecting children from passive smoking, it's about taking smoking completely out of children's lives," Professor John Britton, chairman of the college's Tobacco Advisory Group, which produced the report, said.
Professor Terence Stephenson, the president of the Royal College of Paediatrics, added: "We should be making cars totally smoke-free if there are children travelling in them. We strongly upport the policy recommendations in this report."