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.