A bill banning smoking in cars with children has passed its final reading with support from all parties.
The law makes it an offence to smoke in a motor vehicle carrying anyone under 18 years old.
Police will be able to issue fines of up to $50, however this will not come into effect for 18 months.
Associate Health Minister Jenny Salesa said the ban would mean thousands of children will have healthier lungs.
"We know that second-hand smoke can accumulate in vehicles, even with the windows down," she said.
"That presents an unacceptable risk to kids who never asked to be exposed to second-smoke, and deserve a fighting chance at a life of healthy, clean lungs.
"Our government wants to make New Zealand the best place in the world to be a child. We're making progress towards that goal by putting the interests of kids first."
Salesa said while police would have enforcement powers, the focus would be on educating people.
"It is important to note that enforcement efforts will only focus on public education and changing social norms.
"Police will use their discretion over whether or not to issue an infringement fee, give a warning, or provide information and referrals to the local stop smoking services", she said.
The bill also includes an exemption for people smoking in vehicles that are used as dwellings.
However the scope of the exemption has been narrowed from its first reading and now applies only to vehicles that are designed to be used as dwellings, such as campervans and motor homes, and while they are stationary.
Although National backed the legislation it was highly critical during the debate, with its MPs saying it could have been a much stronger bill.
MP Nicky Wagner said the 18-month delay in enforcement was extremely disappointing.
"So much for this government's stated commitment to protect children, and so much for this government's stated commitment smokefree 2025", she said.
Wagner told the House the exemption for vehicles used as dwellings was illogical.
"Does anyone else think it's odd this legislation says that travelling in a car with a smoker is bad for childrens' health and must be stopped, but living in a car where somebody smokes is A-Okay?", she said.
Wagner also took aim at the government's lack of action on regulation of vaping, and said she would rather see more time and resources focused on helping smokers to quit.