By Natalie Marchant
Around 700 medics and health experts are calling on the government to ban smoking in cars carrying children ahead of a Commons vote on Monday.
In a letter to the British Medical Journal (BMJ), respiratory experts said second-hand smoke is a "major cause of ill health in children".
They say it can damage the developing lungs, cause sudden infant death and lead to thousands of hospital trips every year.
Signatories to the letter are being co-ordinated by Dr Nicholas Hopkinson from Imperial College London.
Health professionals support ban on smoking in cars
As of 8am on Thursday, 692 doctors, nurses and other health professionals and experts had signed up to support the ban on smoking in cars.
Their letter said: "Second-hand exposure to tobacco smoke is a major cause of ill health in children.
"Smoke inhalation damages the developing lung.
"The Royal College of Physicians estimates that each year in the UK it is responsible for 300,000 primary care contacts, 9,500 hospital admissions, at least 200 cases of bacterial meningitis.
'Disease affects disadvantaged children in society'
"Most of this additional burden of disease falls on the more disadvantaged children in society, and all of it is avoidable."
The signatories said those objecting to a change in law assumed there was a "right to force children to breathe tobacco smoke".
Objectors "seem to value this more highly than the children's right to breathe clean air", they added.
They said: "We urge MPs to support this important public health measure, which will protect the wellbeing of children now and in the future."
Commons vote on smoking in cars
The letter comes as a minister announced there would be a Commons vote on the issue on Monday.
Transport minister Robert Goodwill told MPs he would vote in favour of the ban, having been forced to sit in the back of a car as a child while his father smoked.
The vote comes as the Children and Families Bill returns to the Commons.
The Bill was amended in the House of Lords last week after Labour tabled an amendment which would give the Health Secretary the power to make it illegal to smoke in a car carrying children.
Peers have now accepted a government-backed version of the amendment.