Passive smoking causes at least 22,000 new cases of asthma and wheezing in children every year, doctors said today.
More than 20,000 chest infections, 120,000 bouts of middle ear disease and 200 cases of meningitis in youngsters are also thought to be linked to the effects of second-hand smoke, they said.
Funded by Cancer Research UK and carried out by the UK Centre for Tobacco Control Studies, the research found that children whose parents both smoked were almost nine times as likely to be exposed to second-hand smoke as those in non-smoking families.
If the father smoked, then exposure was around three times higher and more than six times higher if the mother smoked.
Children whose parents or brothers and sisters smoked were also 90% more likely to grow up to become smokers themselves.
The doctors added that passive smoking results in more than 300,000 GP consultations, some 9,500 hospital admissions and costs the NHS about £23.3 million, the UK-wide report from the Royal College of Physicians (RCP) said.
Experts behind the report made a series of recommendations, including taking steps to cut the number of adults who smoke, particularly young adults.
They called for increases in the real price of tobacco, measures to tackle tobacco smuggling and illegal trading, and investment in media campaigns targeted at young people.
Cigarettes should also be taken off display in shops while packaging should be made generic and standardised, they said.
Other measures include banning smoking in cars, cutting down exposure to images of people smoking in the media, and stiff penalties for those who sell cigarettes to under-age youngsters.
Professor John Britton, chair of the RCP's tobacco advisory group, said: "This report isn't just about protecting children from passive smoking, it's about taking smoking completely out of children's lives."
Professor Terence Stephenson, president of the Royal College of Paediatrics and Child Health (RCPCH), which is supporting the report, said: "The Royal College of Paediatrics and Child Health has recently led on the call to ban smoking in cars with children travelling in them.
"We should be making cars totally smoke-free if there are children travelling in them.
"Second-hand smoke has been found to be strongly linked to chest infections in children, asthma, ear problems and sudden infant death syndrome, or cot death.
"We strongly support the policy recommendations in this new report and repeat the call for new approaches to address this problem so that we protect the health of children and young people."
In 2003, more than 11,000 people in the UK were thought to have died as a result of passive smoking.
* But what do you think?
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