A ban on smoking in cars carrying children under 16 could be introduced early next year in the Republic.
The Irish department of health is preparing proposals for the new laws, which are also being mooted in other countries.
The move has been welcomed by anti-smoking groups but they warned that legislation will have to be accompanied by a public education campaign.
However, the plans were criticised by a smokers' lobby group, which said it unnecessarily impinged on private space.
Yesterday, Irish health minister James Reilly said he had been considering banning smoking in cars with children in them for some time.
"You are exposing them to sidestream smoke, which is known as being more carcinogenic than the smoke you inhale," he said. "I am in favour of legislation as early as I can next year."
The minister rejected criticism that the legislation was impinging on personal space.
"It is one thing to harm your own health, it is another thing to harm the health of a minor. We see parents smoking with children caught in baby seats in the back, with no escape from a carcinogen. It is highly wrong," he added.
Smokers' lobby group Forest Eireann said smokers were being characterised as "dangerous sick addicts" and the planned legislation was a "joke".
"The suggestion is that they (smokers) have their own children in the car and they are trying to kill them and we have to introduce a law," said spokesman John Mallon
The Irish Cancer Society welcomed the announcement of the planned legislation.
"Children have little choice and cannot leave a smoke-filled car if they want to," its health promotion manager Norma Cronin said.
"But any legislation introduced by government must be supported by a public awareness campaign, similar to the workplace smoking ban which has been highly successful."