A ban on smoking in cars carrying children has come into force in Scotland.

On-the-spot penalties of £100 or a court fine of up to £1,000 can now be handed to anyone caught lighting up in a private vehicle with someone under 18 on board.

A similar ban came into force in England and Wales in October last year. An investigation found just one fine was handed out in the first year of the new law.

Ministers and health campaigners say the move will protect children, but some campaigners called it "patronising and unnecessary".

Sheila Duffy, chief executive of anti-smoking charity Ash Scotland, said the move sends a clear message that children should grow up in a smoke-free environment.

She said: "When we know that just one cigarette can quickly lead to harmful levels of smoke, we have to take action. This is about protecting children's health."

The Smoking Prohibition (Children in Motor Vehicles) (Scotland) Bill was passed unanimously by MSPs almost a year ago. Liberal Democrat MSP Jim Hume, who introduced the bill, said the law could "potentially save 60,000 children a year from the hazards of second-hand smoke".

The Scottish Government said the measure is part of its plans to create a "tobacco-free generation" by 2034, defined as a smoking rate of less than 5%.

Simon Clark, director of the smokers' group Forest, said: "The regulations are patronising and unnecessary. Very few adults smoke in cars with children. Smokers know it's inconsiderate and the overwhelming majority don't do it.

"So few people smoke when there's a child in the car it will be like looking for a needle in a haystack."