A Bill to ban smoking in cars when children are present has passed its first hurdle in the Scottish Parliament.

MSPs unanimously voted to agree the general principles of the Smoking Prohibition (Children in Motor Vehicles) (Scotland) Bill brought forward by Liberal Democrat Jim Hume.

The legislation would bring in fines of £100 for motorists caught smoking in private vehicles while a child aged under 18 is on board.

It had already won the backing of Holyrood's Health Committee, the Scottish Government, Scottish Labour, charities and academics, but concerns have been raised about its enforcement.

The Scottish Conservatives supported the Bill but called for a "sunset clause" to be inserted to ensure it is effective.

Mr Hume told MSPs: "It's estimated that each week in Scotland 60,000 children are exposed to second-hand smoke in cars.

"Numerous studies and reports have shown that there is no safe level of exposure to second-hand tobacco smoke, and in fact in cars the concentration of second-hand smoke toxins can be more than 11 times as high as in a pub.

"Children suffer because of second-hand smoke. The purpose of the Bill is straightforward, it is to protect our children from the harmful effects of exposure to second-hand smoke.

"This legislation is not about raising revenue or forcing people to stop smoking. It is designed to purely prevent acute exposure of children to second-hand smoke and put an end to the anxiety they are subjected to."

Public health minister Maureen Watt said Scotland could be proud of its record as a "world leader" on tobacco control.

She said: "There can be no doubt that we all have a responsibility to protect children from tobacco smoke.

"The Scottish Government supports this legislation and will work with Mr Hume to ensure that it is implemented quickly.

"We must all work together to protect children from the harm of second-hand smoke. There should be no delays in ensuring that protection in law is in place."

Labour's equalities spokeswoman Jenny Marra said the ban on smoking in bars, restaurants and all public places that came into force in 2006 "was never intended to be the last word in our battle to reduce the historically high incidence of smoking".

She said: "It's nearly a decade on now and the figures show that we still have much to do.

"A private vehicle remains one of the few places where children can legally be exposed to tobacco smoke and in such a confined space it poses an obvious health risk.

"The time is absolutely right to correct this anomaly and bring us in line with other parts of the UK."

Conservative health spokesman Jackson Carlaw said: "The Scottish Conservatives support this Bill but there is no point in having such as measure if there is no way of gauging how successful it actually is.

"By adopting a legislative measure, we can give this Bill every chance to succeed and then in a sensible post-legislative debate, after a number of years, review its effectiveness.

"It's an insurance policy if you like. If a measure has proved effective it will be reaffirmed. If not, then it will fall."

Sheila Duffy, chief executive of health charity Ash Scotland, said: "We know that second-hand tobacco smoke is harmful and that it can reach very high levels when someone smokes in a car.

"Scottish survey results indicate around one fifth of 13 and 15-year-olds are exposed to tobacco smoke during car journeys.

"It is pleasing that health interests were joined by the enforcement agencies, Police Scotland and environmental health officers in supporting this Bill. I am confident it will be effective in its goal of protecting children."