A national campaign has been launched by the Government to increase awareness about the dangers of inhaling secondhand smoke.
Adverts will run on TV showing that smoking out of a car window or the backdoor is not enough to protect children from secondhand smoke.
The campaign highlights figures from the Royal College of Physicians revealing that over 800 children visit their doctor every day because of exposure to secondhand smoke. The cost to the NHS each year for treatment, hospital and GP visits for illnesses related to secondhand smoke is £23.6 million.
The Government wants smokers to be aware of the increased risk to children of lung disease, meningitis and cot death.
While 80% of secondhand smoke is invisible and odourless, the campaign warns that it contains cancer-causing toxins and poisons.
Despite the risks, a survey by OnePoll in May of over 600 parents who smoke found that 68% had smoked in the car with their children present.
Three-quarters of those surveyed were shocked to learn that secondhand smoke was affecting the health of so many children.
The campaign is urging parents who smoke to keep their homes and cars completely smoke free.
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.
"Secondhand smoke can be an invisible killer and with around 300,000 children seeing their GP each 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."