A bid to make smoking in vehicles when children are present illegal has been launched by an MSP.
South of Scotland Liberal Democrat MSP Jim Hume wants to introduce a members bills at the Scottish Parliament which would bring in a ban.
He has opened a public consultation on his proposals which he says would safeguard the rights of children.
Several health organisations back the ban but a smokers' campaign group said the law would be unenforceable.
The proposed ban is being supported by ASH Scotland and the British Lung Foundation.
The British Lung Foundation had previously urged Scottish politicians to do more to stop people smoking in cars when children are passengers.
In 2011, a Scottish study suggested air quality inside a smoker's car was comparable to industrial smog in cities such as Beijing or Moscow - even when the driver had windows open.
Research by the University of Aberdeen found that 7% of 11-year-olds experience smoking in cars.
Speaking after the launch of his consultation, Mr Hume said: "These proposals have already had an encouraging response from MSPs across the political parties and from people across Scotland.
"Seventeen per cent of children in the UK are legally exposed to passive smoking in a vehicle more than once a week.
"Banning smoking in cars whilst children are present is a further step in protecting children's rights and ensuring they have the healthiest start in life.
"With figures showing eight out of 10 Scots already support such a move, this is a conversation we need to have and an issue which we need to address.
"The time has come to follow the lead of countries like Canada and Australia where similar bans are operating successfully."
The consultation will run until August after which Mr Hume must get cross-party support to take the proposals further.
However, campaigners criticised the proposed bill.
Simon Clark, director of the smokers' group Forest, said: "We don't encourage adults to smoke in cars carrying children but legislation is disproportionate to the problem.
"Most smokers are sensible enough to know that lighting up in a car with children is inconsiderate at best and research suggests that only a tiny minority still do it.
"Education has to be better than yet another law that would be very difficult to enforce."
He added: "A ban on smoking in private vehicles would represent a major intrusion into people's private lives. What next, a ban on smoking in the home if children are present?"
In response, James Cant, head of the British Lung Foundation Scotland, pointed to a 2010 NHS study in England which found that about 18% of children aged 11 to 15 were exposed to smoke in cars.
He said: "NHS research shows that around one in five children are regularly exposed to cigarette smoke in the car, so any suggestion that this is just a minority problem stands in stark contrast to the evidence."