Hundreds of thousands of children could be saved from being exposed to second-hand smoke in cars after MPs paved the way for legislation which could see an end to the practice.
Leading medical charities have said they are "delighted" that MPs voted in favour of outlawing smoking in vehicles carrying children.
The Commons have given the health secretary the power to impose a ban despite the opposition of some MPs, including members of the Cabinet.
Ministers were granted a free vote on the measure - successfully introduced by Labour in a House of Lords amendment to the Children and Families Bill - meaning they are not tied to a party line.
Dr 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.
"The introduction of a law that would help prevent hundreds of thousands of children from being exposed to second-hand smoke in the car is now within reach.
"With both Houses of Parliament having made their support for the ban clear, the onus is now on the Government to act accordingly and make this crucial child protection measure law at the earliest opportunity."
The charity estimates that in England more than 430,000 children aged 11 to 15 are exposed to second-hand smoke in cars every week.
Research published by the organisation last year concluded that 185,000 children of the same age are exposed to smoke while in the family car on "most days", if not every day.
Prime Minister David Cameron missed the vote while visiting flood-stricken areas in the south west.
Mr Cameron's official spokesman declined to say which way the Prime Minister would have voted had he been able to attend Parliament.
But he told a regular Westminster media briefing: "While he understands the concerns that some have expressed, his view is that the time for this kind of approach has come."
Deputy Prime Minister Nick Clegg has spoken out against attempts to "sub-contract responsible parenting to the state" and pro-smoking groups have branded it an "unnecessary intrusion".
Shadow public health minister Luciana Berger welcomed the result but warned ministers not to "kick this into the long grass".
She said: "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.
"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.
"A time-limited consultation may be necessary on the practical details of implementation, but we will be watching closely to ensure the Government don't try and kick this into the long grass."
AA president Edmund King said: "MPs have said, no buts about it, endangering a child's health by smoking in the same car is unacceptable. The dangers from smoking in cars have long been recognised, such as distraction, littering and causing fires.
"These have been dealt with under existing laws but enforcement has proved difficult except after an incident. However, cases of people caught by speeding and other enforcement cameras while reading at the wheel, making V signs and other bad driving, mean that it is quite possible that smoking at the wheel with a child on board may be spotted.
"As has been the case with enforcing the ban on hand-held phones while driving, campaigns and legislation have been shown to reduce illegal behaviour afterwards. If a new law manages to make more adults think twice before lighting up with the kids on board, it will have helped."
But Simon Clark, director of the smokers' group Forest, said he was "disappointed but not surprised" by the decision.
He added: "The Government has been spineless in its response to Labour's initiative.
"Legislation will have very little impact because so few adults still smoke in cars carrying children. Those that do will carry on because it will be very difficult to enforce.
"The overwhelming majority of adult smokers know how to behave towards children and the law should reflect that.
"It shouldn't be used to stigmatise them as potentially unfit parents who can't be trusted to do the right thing without state intervention.
"If you believed everything you heard in the House about the threat to children's health it's a miracle anyone who was a child in the fifties and sixties, when a large majority of adults smoked, is still alive.
"Government has banned smoking in public places. Now they're going to ban it in a private place. The home will be next."
Deborah Arnott, chief executive of health charity Ash (Action on Smoking and Health) said: "This is an historic victory for Parliament and for children's health.
"With support from across all political parties legislation has passed now both through the House of Lords and the Commons which will ensure cigarettes can be put in plain standardised packaging and smoking in cars with children under 18 can be made illegal."
Professor John Britton of the Royal College of Physicians tobacco advisory group, added: "Second-hand smoke has been strongly linked to a whole host of adverse health effects amongst children, including chest infections, asthma, ear problems and sudden infant death syndrome.
"Exposure to second hand smoke in cars is particularly dangerous as it is a confined space leading to a high concentration of smoke.
"The introduction of a ban on smoking in cars with children will be a big step forward in protecting our children from the harm caused by passive smoking."
The British Medical Association (BMA) has campaigned for a ban since 2011.
Professor Sheila Hollins, chairwoman of the BMA's Board of Science, said: "The outcome of this resounding vote is an important step forward in reducing tobacco harm by stopping children from being exposed to second-hand smoke in private vehicles.
"Children are still developing physically and, as a result, they are more susceptible to the harmful effects of second-hand smoke.
"Adults who smoke in the presence of children are not acting in the children's best interest; therefore it is the Government's duty to change legislation in order to protect them."