Drivers who smoke while carrying passengers under the age of 18 will face a £50 on-the-spot fine from October as a result of legislation passed this week.
Smoking in cars which are carrying children will be banned in England and Wales from the autumn.
This week MPs in London and Welsh ministers have decided that smoking at the wheel while under-18s are present is to be outlawed.
Children face higher risk
The ban will come into effect on 1 October 2015.
Drivers who flout the new law will face an on-the-spot fine of £50.
The legislation is the result of pressure from campaigners who say that second-hand smoke is more dangerous to children than to adults due to their smaller lungs and faster breathing.
And passive smoking in a confined space such as a car is thought to increase the health risks further.
Dr Penny Woods, chief executive of the British Lung Foundation, said: "Having campaigned on this issue for many years, we’re absolutely delighted that MPs have overwhelmingly backed the ban on smoking in cars carrying children.
"MPs from across the parties have come together to support this ground-breaking measure."
The British Lung Foundation says that roughly 185,000 children between the ages of 11 and 15 are exposed to smoke in their families’ cars on most days of a typical week.
Professor Dame Sally Davies, Chief Medical Officer, said: "The passing of regulations to make smoking in cars carrying under-18s illegal is a significant victory for protecting children’s health from second-hand smoke.
"Smoking just a single cigarette in a car exposes children to high levels of air pollutants and cancer-causing chemicals like arsenic, formaldehyde and tar.
"Children are least equipped to speak out to protest against secondhand smoke, so I welcome this legislation to end smoking in cars when they are present."
In England, the law was originally added by Labour to the Children and Families Bill at the start of 2014.
Politicians in Cardiff, meanwhile, had been running an educational campaign to warn drivers of the potential dangers of second-hand smoke for youngsters.
'A step too far'
But it was felt that this had not been sufficiently effective in reducing the number of motorists who smoked while transporting their children and that stronger measures were necessary.
Smokers’ rights group Forest, however, said the ban was a step too far.
Director Simon Clark said: "The overwhelming majority of smokers know it's inconsiderate to smoke in a car with children and they don't do it. They don't need the state micro-managing their lives.”
Clark added that a further problem was that the police would be unable to enforce the law effectively.
"The government will need a small army of snoopers to report people," he said.
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