More than 800 children visit their doctor every day suffering from the serious effects of breathing in second-hand smoke, according to a new report.
The figures have been highlighted as the Government launches a campaign to increase awareness of the hidden dangers of smoking in homes and cars.
According to research by the Royal College of Physicians, more than 80% of second-hand smoke is invisible, odourless and contains harmful cancer-causing toxins and poisons.
TV adverts will show that smoking out of a car window or the back door is not enough to protect children from second-hand smoke.
Chief Medical Officer Professor Dame Sally Davies said: "It's well known that smoking kills, but many smokers still don't realise the damage their smoke causes to those around them.
"Second-hand smoke can be an invisible killer and with more than 300,000 children seeing their GPeach year because of it, we need to make sure people know how dangerous it can be.
"Our message is clear: giving up smoking is by far the best way to protect your family and we can help you quit to give you and your loved ones a healthier future."
A survey of nearly 700 parents conducted this month revealed some worrying trends.
Of those asked, 68% of parents admitted to smoking in the car with their children present.
Mum-of-two and part time social worker Laura Miller, from Rochdale, used to smoke 20 cigarettes a day and says she often smoked around her children.
She gave up after getting help from a local NHS quitting service.
"I used to smoke at the back door thinking I was getting away with it, but then I'd go back inside pick up the baby and the smoke was in my hair and clothes - everywhere.
"I noticed the baby was starting to get a cough and that's when I thought enough was enough."
Dr Harpal Kumar, CEO of Cancer Research UK said: "The evidence is clear. Smoking around children is harmful, especially in homes and cars, so it's vital they are protected from the dangers of second-hand smoke."
Smokers can visit here to order a free Smokefree Kit. Facts, tips and tools are also available on the site to help them on the way to a smoke-free future.
source: Uk news