Child seat-belts in cars are law - should a smoking ban be added?
Adults should be banned from smoking in cars when children are passengers, the new head of the Royal College of Paediatrics and Child Health has said.
In a BBC News website Scrubbing Up column, Professor Terence Stephenson, said children deserved protection.
"You can't inflict this on your colleagues any more. Why should we treat our children's health as a lower priority?" he said.
A Department of Health spokesman said it would review smoking laws next year.
Professor Stephenson, who recently took over as head of the college, said children should not have to breathe in their parents' cigarette smoke.
"Why on earth would you light up in your car whilst your children are sitting happily in the back?
"On the assumption that you wouldn't pass the packet round and invite the kids to light up, why make them breathe tobacco smoke at all?"
He said the Canadian province of New Brunswick, California, South Australia and Cyprus had already introduced such legislation successfully.
And Professor Stephenson said second-hand smoke had been linked to chest infections, asthma and ear problems in children.
Deborah Arnott, chief executive of the anti-smoking charity Action on Smoking and Health (ASH), backed a complete ban on smoking in vehicles.
"Cars are small tin boxes, with not much air in them.
"Smoking just one cigarette, even with the window open, creates a greater concentration of second-hand smoke than a whole evening's smoking in a pub or a bar.
"That's not just bad for children but for adults too, especially those who already have heart or lung diseases."
And a spokeswoman for the road safety charity, Brake, said smoking while driving meant people were not concentrating on the road.
"All that can add up to not having proper control of your vehicle or dangerous driving."
She said it might be useful to have a law banning smoking in the same way there was in force regarding using hand-held mobile phones.
But Neil Rafferty, Scottish spokesman for Forest, the pro-smokers' rights group, said: "We don't think that children should be exposed to smoke in a car but a ban would be a waste of police and court time.
"Would it be OK if you opened the sunroof or a window while smoking? It's an impractical suggestion.
"People like those at the Royal College of Paediatrics and Child Health should be more realistic about what is possible."
A Department of Health spokesman said it would look at whether current anti-smoking laws needed to be extended.
He added: "We would always strongly recommend that people do not smoke in cars, especially those used to transport children."