Smoking should be banned in cars to protect drivers and passengers – especially children – from breathing in toxins far worse than those found in smoky bars, the nation's doctors have demanded.

The British Medical Association (BMA) is urging ministers across the UK to extend the ban on smoking in public places introduced in 2007 to all vehicles in a further effort to protect people's health.

Children are at particular risk from secondhand smoke in cars because they take in more of the chemicals from cigarettes than adults and may not be able to refuse to travel in a smoky car.

The BMA called for a ban after reviewing previously published research studies into cars and smoking.

A car's occupants could be exposed to 11 times more toxins than they would encounter in a smoky bar, the BMA's review found [see footnote]. Older people, who are more likely to have breathing problems, are also at extra risk of health damage from inhaling secondhand smoke in a car, it added.

The government is unlikely to do what the BMA recommends, though. "We do not believe that legislation is the most effective way to encourage people to change their behaviour," a Department of Health spokesman said.

But the BMA hopes that the devolved administrations in Edinburgh, Cardiff and Belfast, which are pursuing some innovative public health measures such as alcohol minimum pricing and presumed consent organ donation, might take their own action.

"We are calling on UK governments to take the bold and courageous step of banning smoking in private vehicles," said Dr Vivienne Nathanson, the BMA's head of science and ethics. "The evidence for extending the smoke-free legislation is compelling."

The all-party parliamentary group on smoking and health is calling for ministers to hold a public consultation on how to tackle smoking in cars. While opinion polls show widespread support for banning smoking in cars carrying children, such a step would be hard to enforce and would not protect adults, the MPs and peers say.

The British Lung Foundation said it would support such a ban because children "are literally trapped in the car and have no choice but to breathe in smoke".

The Royal College of Paediatrics and Child Health also backs more limited action.

But David Cameron, an ex-smoker, recently signalled his opposition to a car ban. He praised the success of the public places smoking ban, which he opposed at the time, but added: "I am much more nervous about going into what people do inside a vehicle," he told Labour MP Alex Cunningham, who is trying to get parliament's backing for a private member's bill outlawing smoking in child-carrying cars.

The health department will next year launch a marketing campaign in England to publicise the risks of secondhand smoke as part of its efforts to encourage even fewer people to smoke, a spokesman said.

• This article was amended on 1 December 2011 in line with a correction issued by the BMA after the article was published. The original said that a car's occupants were exposed to 23 times more toxins than they would encounter in a bar.