The DUP has voted against a ban on smoking in vehicles carrying children – despite the DUP Health Minister in the Assembly suggesting he would support one here.
Yesterday MPs voted overwhelmingly to approve a plan to ban smoking in cars where children are passengers.
Any law would only apply to England and health campaigners quickly threw down the gauntlet to politicians here.
The Northern Ireland Chest, Heart and Stroke (NICHS) charity has said it hoped the vote would "galvanise" the Assembly.
Spokesman Andrew Dougal said: "It is essential that Northern Ireland children are afforded the same protection as those in England."
And the British Lung Foundation called on Northern Ireland's politicians to speed up a planned bill to do the same.
Dr James Cant, head of British Lung Foundation Northern Ireland, said: "Congratulations to England and Wales – they've thrown down the gauntlet, and now Northern Ireland's politicians must pick it up."
The SDLP's Mark Durkan and Margaret Ritchie supported the ban, as did independent North Down MP Lady Sylvia Hermon.
Northern Ireland Secretary Theresa Villiers opposed a ban, alongside DUP MPs Ian Paisley jnr and Jeffrey Donaldson.
In 2011, DUP Health Minister Edwin Poots launched a public consultation on smoking in cars.
He told the Assembly at the time: "Passive smoking is a health issue which I take very seriously, particularly when those affected by it are children, who are more vulnerable to secondhand smoke than adults."
The DUP also agreed the impact of secondary inhalation increased the risk of asthma, bronchitis and other respiratory conditions in children and young people.
South Down MP Ms Ritchie said: "It is abuse and must be tackled." David Cameron missed the vote while visiting flood-stricken parts of England.
His official spokesman declined to say which way the Prime Minister would have voted.