"Peers have backed plans to ban smoking in cars when children are present, but supporters admit they do not have government backing for the move.
The House of Lords approved Lord Ribeiro's private member's bill to make offenders liable for a £60 fine or attendance at a smoke awareness course.
The measure would need the support of MPs to become law and David Cameron has questioned whether it is justified.
He has suggested it would have serious implications for personal freedoms.
Mr Cameron told MPs last year that while he backed the ban on smoking in pubs, he felt "more nervous" about proscribing what people should and should not do in private vehicles.
'Raise the ante'
Parliament needed to have a "serious think" before taking such a step, he added.
The Lords voted through Lord Ribeiro's bill - which was backed by many health campaigners and charities - on the nod on Monday.
The Conservative peer said there was not strong government support for legislation in the area, with ministers favouring education as a way of persuading parents to change their behaviour.
He said most smokers did not do so while driving their children but there was a "hard core" of parents whose behaviour had to be addressed.
The proposed legislation would "raise the ante" over the issue and remind ministers there were other options should their approach not succeed in protecting children from harm.
Labour MP Alex Cunningham introduced legislation urging a ban in the Commons last year but despite clearing its first legislative hurdle, it faced significant opposition from MPs of all parties."
http://www.bbc.co.uk/news/uk-politics-18963680
