Drivers in England will be banned from smoking in their cars if they are carrying children as passengers.
The move, which will become law on 1 October, follows a similar ban in Wales and aims to protect young people under 18 from second-hand smoke. Scotland is also considering introducing a ban.
Anyone found flouting the law in England could be fined £50.
The British Lung Foundation welcomed the ban as a victory, but smokers' group Forest said it was unenforceable.
It will not apply to anyone driving alone or driving in a convertible car with the top down.
The regulations were passed in the Commons after 342 MPs voted in favour of legislation while just 74 voted against.
More than 430,000 children are exposed to second-hand smoke in cars each week, according to the British Lung Foundation,
Passive smoke in children can increase the risk of asthma, meningitis and cot death, say public health experts.
'Important step'
Public Health Minister, Jane Ellison, said: "Three million children are exposed to second hand smoke in cars, putting their health at risk.
"We know that many of them feel embarrassed or frightened to ask adults to stop smoking which is why the regulations are an important step in protecting children from the harms of secondhand smoke."
Dr Penny Woods, chief executive of the British Lung Foundation, said: "This is a tremendous victory.
"We urge the Government to show the same commitment to introduce standardised packaging for all tobacco products, in order to protect the 200,000 children taking up smoking every year in this country.
"We are certain that these measures together will prove to be two of the most significant milestones for public health since the smoke-free legislation of 2007."
But Simon Clark, director of the smokers' group Forest, said the legislation was excessive.
"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," he said.
"The police won't be able to enforce the law on their own so the government will need a small army of snoopers to report people."
