A campaign to stop people smoking in cars when children are travelling has been launched by the Welsh government.

Fresh Start aims to protect youngsters from the effects of second-hand smoke in a confined space.

An outright ban will be considered depending on the success of the three-year campaign.

But Simon Clark from the lobby group Forest said that a ban would be expensive, a step too far and totally unnecessary.

Launching the campaign, chief medical officer for Wales Dr Tony Jewell said children in cars were particularly at risk from second-hand smoke.

"Exposure to these chemicals puts children at risk from a range of conditions, including sudden infant death syndrome and asthma," he said.

"There is robust evidence that the level of toxic chemicals is very high in cars, even with a window open. The Fresh Start Wales campaign aims to make people aware that smoking in cars is dangerous for their passengers, particularly children."

Analysis Accusing parents of poisoning their children might seem like an extreme measure - but there seems to be a fair deal of sympathy for this campaign amongst smokers. Even the lobby group Forest describes smoking in a car with a child as 'inconsiderate' - but it draws the line at any suggestion of a ban. Any legislation would bring several sticking points - not least the question of how it could be enforced. The BMA has called for a total ban on smoking in cars, regardless of the occupant's age. It argues older people are also at risk when inhaling second-hand smoke. But would the public be persuaded? The Welsh government has settled on a wait and see approach in the hope that their campaign will prove to be an effective way of cutting smoking rates.

First Minister Carwyn Jones said smoking in cars "poisons" children and Wales would not shy away from further legislation.

"A ban on smoking in cars carrying children will be considered later in this five-year term of government if smoking levels do not reduce as a result of the campaign," he said.

"We have commissioned research to measure levels of smoking in cars and public attitudes towards it, which will be revisited throughout the campaign to evaluate its success."

But Mr Clark, of tobacco lobby group Forest, said: "I disagree that they're poisoning children but I support the campaign.

"I think it's important to encourage parents not to smoke in a car where small children are present out of consideration for the child if nothing else."

Mr Clark wanted an assurance from the Welsh government that a ban would not be introduced.

"We think that would be a step too far and totally unnecessary," he said.

"And I think it's outrageous at the way they're treating smokers considering there are 10m smokers throughout the United Kingdom who contribute a massive amount to tobacco taxation - over £10bn a year.

"It's a perfectly legal product and I think it's quite wrong the way smokers have been treated."

SMOKING FACTFILE One in four adults (23%) in Wales smokes, with rates higher in more deprived areas.

11% of 15/16 year old boys and 16% of girls smoke.

You Gov Survey for Ash Wales found that four in five Welsh adults strongly agreed or agreed smoking should be banned in cars carrying children younger than 18

Smoking in cars is banned in Mauritius whether or not children are present

Nine out of the 10 provinces in Canada and six states in Australia have banned smoking in cars Source: Welsh Government

Dr Iolo Doull, from the Royal College of Paediatrics and Child Health officer for Wales, who has previously called for a total ban in cars, backed the campaign.

"Infants and children exposed to tobacco smoke are more likely to have chest infections, to have ear infections, to be admitted to hospital with wheezing or asthma, and to die of cot death," he said.

Chris Mulholland, head of the British Lung Foundation Wales, said it was vital that the option of a ban remained.

"Poll after poll shows a huge majority of the public would support a ban," she said. "Evidence from other countries shows that legislation has made a big difference in protecting children."

But a spokesman from the motoring organisation the AA questioned how any future ban would be enforced.

"I think it would be done domestically," he said.

"Once you've got a rule there it's easy for mum to tell dad to stop smoking in the car or for granny to tell granddad and so on.

"I don't think it's high on a traffic police officer's list of priorities."