MPs in Worcestershire were divided on whether smoking should be banned in cars carrying children - with one parliamentarian saying police have better things to do.
West Worcestershire Harriett Baldwin, who was promoted to Government assistant whip on Saturday, voted against the ban last night, saying there are major crimes police need to focus on.
However Worcester's Robin Walker, Mid-Worcestershire's Peter Luff and Mark Garnier, who represents the Wyre Forest, all backed it.
The vote - passed by 376 votes to 107 - means the Government now has powers to bring in the crackdown for the first time ever.
Mr Walker said: "The public health concerns around smoking are very clear.
"I do think police have had a hard time enforcing the ban on mobile phones, but I don't think anyone can argue that this won't be a good thing.
"On balance I support the ban as the fact it may be difficult to enforce isn't a reason to not vote for it."
Mr Luff took the unusual decision of asking his 5,100 Twitter followers what he should do.
He said the tweet led to "100 per cent support" from constituents in favour of a ban.
"The constituents told me the freedom of children to enjoy good health trumps all other arguments," he said.
"It didn't make my mind up for me, but it informed my view.
"It's about protecting the vulnerable and making sure children are not passive smokers."
The Coalition decided to give MPs a free vote on the debate last night, meaning they were not asked to back the views of their respective party leaders.
Mrs Baldwin said she would prefer police to concentrate on other crimes like drugs, metal theft and burglaries.
"I am against smoking in cars with children but do not think it should be illegal," she said.
"I would prefer the police focus their time on drug related crime, catalytic converter thefts, metal theft and rural burglaries."
MPs voted in favour of an amendment to the Children and Families Bill, which empowers ministers to bring in a ban in England.
Prime Minister David Cameron missed the vote because he was visiting flood stricken parts of the South West, but Downing Street now says it will legislate for the ban.