Guernsey’s ban on smoking in cars carrying children aged under 18 comes into force on 1 November.
The States decided in May to make “smoking a tobacco product in an enclosed motor vehicle carrying a child” a criminal offence.
Guernsey Police said the offence would carry a Band C fixed penalty notice of £125, or £115 if paid within seven days.
Lucy Cave, from the Health Improvement Commission, said if legislation was not in place “people then assume, wrongly, that there is less of a danger or that there is less harm.”
Smoking in cars carrying children has been illegal in England, Wales and Jersey since 2015.
Guernsey deputies published the new law in September 2024 and it was passed in the States Assembly on 23 October.
But Simon Clark, director of the UK smokers’ lobby group Forest, said he did not see the point of the legislation.
“We’ve always felt that legislation is a step too far, it’s unnecessary,” he said.
“We’ve seen over several decades that smokers have changed their behaviour, and especially around children, and they should get some credit for that, not another law dictating how they behave.”
Jersey Police has said it can not confirm how many, if any, fines have been issued for breaching the ban.
It said “Our primary focus has always been on educating the public about the dangers of smoking in cars with minors rather than strictly enforcing penalties.”
Senior Lecturer of Public Health at Imperial College London, Anthony Lavery, wrote a research project looking into the effects of the legislation brought in in England in 2015.
It found that fewer children were exposed to second-hand smoke following the law.
Mr Lavery said “The main aim of the law is to reduce the exposure of children to second-hand smoke so it’s not to see more people convicted.”
Health and Social Care and Guernsey Police have been approached for comment.