Image copyright PA Image caption Parliament had spoken and a ban would happen, the Downing Street source said

The UK government will make it a criminal offence to smoke in cars in England when children are passengers, a Downing Street source has said.

MPs voted in favour of an amendment to the Children and Families Bill, which empowers, but does not compel, ministers to bring in a ban in England.

The source told the BBC that Parliament had spoken and a ban would happen.

The vote - passed by 376 votes to 107 - also gave the Welsh government the power to bring in a ban in Wales.

The liberty to smoke in your car in front of a child doesn't seem to me that important and protecting a child's health does seem to me to be incredibly important Norman Lamb, Health Minister

Welsh ministers must now decide if they want to make smoking in cars carrying children illegal in Wales.

Liberal Democrat Health Minister Norman Lamb, speaking to BBC Radio 4's World Tonight programme on Monday, said he hoped a ban would be established.

He said the majority of 269 was "so decisive that I think there's a very clear mandate now to get on and legislate, but we will have that discussion".

He added: "You have to ask yourself the question, 'How important is the liberty that we're infringing here?'

"The liberty to smoke in your car in front of a child doesn't seem to me that important and protecting a child's health does seem to me to be incredibly important."

'Great victory'

After the debate, shadow public health minister Luciana Berger warned ministers not to "kick this into the long grass".

Smoking in cars Smoke can stay in the air for up to two and a half hours even with a window open.

Second-hand smoke contains more than 4,000 chemicals, some of which are known to cause cancer.

Exposure has been strongly linked to chest infections, asthma, ear problems and cot death in children.

Research indicates that 300,000 children in the UK visit a GP each year because of the effects of second-hand smoke, with 9,500 going to hospital.

Smoking in a car creates a higher concentration of toxins than in a bar. Some research has put it at 11 times higher.

Bans on smoking in cars when children are present already exist in some US states, including California, as well as in parts of Canada and Australia.

"This is a great victory for child health, which will benefit hundreds of thousands of young people across our country. It is a matter of child protection, not adult choice," she said.

She added: "The will of Parliament has been clearly expressed today and this must be respected.

"Ministers now have a duty to bring forward regulations so that we can make this measure a reality and put protections for children in place as soon as possible."

Neither Health Minister Jane Ellison, in the House of Commons, nor a Department of Health spokesman gave any commitment.

Opening the debate on Monday evening, Ms Ellison said only: "We will see what the view of the House is and we will take our steer on the principle of the issue then having heard the views of both Houses."

The House of Lords passed the amendment last month. The bill returned to the Commons on Monday for debate.

'Absolutely delighted'

The government gave its MPs a free vote in the Commons on the issue.

We have consistently stated that we will consider the possibility of legislation once we have fully evaluated the impact of the campaign Welsh government spokesperson

Prime Minister David Cameron missed the vote because he is staying in the South West overnight to visit areas affected by flooding.

Penny Woods, chief executive of the British Lung Foundation, said: "Having campaigned on this issue for many years, we're absolutely delighted that MPs have backed the ban on smoking in cars carrying children. This could prove a great leap forward for the health of our nation's children."

But Simon Clark, director of smokers' lobby group Forest, said smoking in cars with children was "inconsiderate", but there was "a line the state shouldn't cross when it comes to dictating how people behave in private places".

After the Commons vote, a Welsh government spokesperson said: "We have consistently stated that we will consider the possibility of legislation once we have fully evaluated the impact of the campaign.

"We have commissioned studies of children's exposure to second-hand smoke in cars and results will be available later this year."

In Scotland, Liberal Democrat MSP Jim Hume has indicated he will be presenting a bill this year to bring in a ban, while Northern Ireland's health minister has announced plans for a consultation on the issue.