The British Lung Foundation Charity says that more than 430,000 children aged 11-15 are exposed to second hand smoke in their family cars at least once a week.
The figures come as the House of Lords prepares to debate whether to ban smoking in cars where children are present.
The figures come from a poll of 7,500 secondary school children and 6% were exposed to smoke and a further 8% said they were exposed to smoke in their families cars once or twice a week.
BLF director of research Dr Noel Snell said: ”Adults are protected from second-hand smoke in public places and in work vehicles. This amendment is fundamental to child protection and must be passed in the Lords if we are to help shape a healthy future for this generation of children,”
Simon Clark, director of Forest, said: “According to surveys, only a very small number of adults still smoke in cars with children present. It’s inconsiderate and most adults recognise that.
“Legislation is disproportionate to the problem. It would be very difficult to enforce and would be a huge waste of police resources.
“Education has to be better than coercion.”