But Health Minister Lesley Griffiths confirmed a campaign will run about the effects of second-hand smoke in cars.
An action plan to reduce the harm caused by smoking also includes moves to ban smoking on NHS premises and in children's playgrounds.
David Bowden, from The Institute of Ideas, said any ban would not be right.
Ms Griffiths rejected calls from Plaid Cymru to bring in rules sooner to make smoking in cars carrying children illegal.
But the minister said the Welsh government will launch a three-year education campaign about the effects of second-hand smoke in cars.
Ms Griffiths said the government will "consider bringing forward legislation," if evidence shows the campaign fails to achieve a significant reduction in exposure to second-hand smoke.
David Bowden, from the civil liberties think-tank The Institute of Ideas, said most people were aware of the dangers of smoking.
But he said it was not right for governments to decide to ban smoking in playgrounds and in cars.
"We either give individuals the choice to make their own moral responsibility to have bad habits which the government may not approve of, or we don't at all," he told BBC Radio Wales.
Professor Laurence Moore, a director at Decipher, a public health research centre of excellence at Cardiff University, said: "If the government can take firm action it can really help to encourage people not to take up smoking."
Legislation to stop people from smoking in cars carrying children will not be introduced during this assembly term, the Welsh government has decided.