Any parent smoking in the car, even with windows open, is putting their child in highly "unsafe conditions" according to researchers from the University of Aberdeen.
Having revealed that 58% of smoking journeys put passengers in an environment three times above the World Health Organization's 'safe air' limits, study lead Dr Sean Semple said "there is a clear need for legislation to prohibit smoking in cars where children are present".
The British Medical Association have supported the finding revealed in the Tobacco Control journal and called for all smoking in cars to be banned.
Dr Semple added: "The evidence from this paper is that second-hand smoke concentrations in cars where smoking takes place are likely to be harmful to health under most ventilation conditions.
"Children are particularly susceptible because they have faster breathing rates, a less developed immune system and are largely unable to escape or avoid exposure to second-hand smoke."
Using a device strapped to the back seat of the car, the researchers logged and then analysed air quality data during 85 journeys ranging from about 10 minutes to an hour in duration - in 49 of those the driver smoked up to four cigarettes.
During these journeys, levels of fine particulate matter averaged 85µg/m3, which is more than three times higher than the 25µg/m3 maximum safe indoor air limit recommended by WHO.
Even if the driver smoked only one cigarette and had the window wide open, particulate matter levels still exceeded the limit at some point during the journey.
However, Simon Clark, director of the smokers' lobby group Forest, says: "We don't encourage adults to smoke in a car if small children are present, out of courtesy if nothing else, but we would strongly oppose legislation to ban smoking in cars.
"According to research, 84% of adults don't smoke in a car with children present so legislation to ban it would be disproportionate.
"Parents must be allowed to use their common sense, and most of the time they do. There is no need for further regulation."
Estimates from the Royal College of Physicians Tobacco Advisory Group, suggest that last year passive smoking in children accounted for more than 20,000 cases of lower respiratory tract infection, 200 cases of bacterial meningitis, and 40 sudden infant deaths.
Posted 16/10/2012 by firstname.lastname@example.org