A law that prohibits smoking in cars carrying children below the age of 18 has came into effect in England and Wales. Law requires people to abide by it and the defaulters could face a penalty of £50.

Police said that initially they will be taking a non-confrontational approach with the defaulter. They said that whenever an under-18 is in the car, smokers will still be liable even if the windows are down or sunroof open. But the law will not apply to people who are driving in a convertible which has the roof down, they said.

There are higher possibilities that the Scottish Parliament will consider banning smoking in cars carrying children in next year. More than 430,000 children are exposed to second-hand smoke in cars each week, according to the British Lung Foundation.

As per experts, smoke can stay in the air for up to two and a half hours even with a window open. Second-hand smoke contains more than 4,000 chemicals, some of which are known to cause cancer, they said.

Exposure to second-hand smoke has been strongly linked to chest infections, asthma, ear problems and cot death in children.

A National Police Chiefs' Council spokeswoman said in a statement that police officials will be taking an educational, advisory and non-confrontational approach when enforcing the new legislation.

"This would see people being given warnings rather than being issued with fines, which would give time for public awareness of the offences to build", it said.

"The overwhelming majority of smokers know smoking in a car carrying children is inconsiderate and they don't do it.

"If drivers are spotted smoking will they be stopped in case there's a child in the back? The authorities, especially the police, must have better things to do."