Sefton Central Labour MP Bill Esterson says smoking in cars in the presence of children should be banned.
The MP has proposed an amendment to the Children and Families Bill in which he calls for the in-car smoking ban.
Bill, who sits on the Children and Families Bill committee, proposed the ban on child welfare grounds.
Bill said: "Smoking kills. Passive smoking kills We know that. So how can we reasonably endorse people smoking in the presence of children in the confined space of a car?
"Research shows that 300,000 children in the UK visit the GP each year due to second hand smoke - 9,500 visit the hospital.
"Smoking in a car creates a higher concentration of toxins than in a bar. Some studies put it at 11 times higher.
"It cannot possibly be acceptable therefore to expose our children to that. We don't allow smoking in pubs so why in cars when children are present?
"Children are particularly vulnerable to second-hand smoke due to their higher breathing rate, their less well-developed airways, lungs and immune system. Those children who are exposed to second-hand smoke are more at risk of respiratory illnesses, asthma, meningitis and even cot death.
"It's perfectly obvious that it should be banned."
Bill said Britain was lagging behind many other countries in introducing legislation to ban smoking in cars.
Bill said: "Lots of other countries already have this ban of smoking in a car in the presence of children.
"A number of other countries have outright bans on smoking in cars at all. The safety implications are obviously huge.
"While the Highway Code regards smoking while driving a distraction which should be 'avoided' I would argue that lighting a cigarette while driving is as dangerous as using a mobile phone while driving.
"There should be an outright ban.
"But the first step is to get a ban on smoking in vehicles carrying children. We cannot allow our children to be exposed - particularly in confined spaces - to the toxins of second-hand smoke and I am hopeful that my amendment to the Children and Families Bill will get support.
"I wouldn't want my children in a car filled with toxic smoke fumes. And I think the law should be there to protect them and all our children from such dangers."