Passive smoking is a "substantial public health hazard," expert advisers have told the government in a boost to those seeking tobacco bans in restaurants, bars and other work and public places.
A report leaked yesterday is said to conclude that knowledge of the hazardous nature of second-hand smoking has consolidated in the past five years and "this evidence strengthens earlier estimates of the size of the health risk."
It added: "This is a controllable and preventable form of indoor air pollution. It is evidence that no infant, child or adult should be exposed to second-hand smoke."
The conclusions of the scientific committee on tobacco and health (Scoth), reportedly reached in April, have yet to be officially published, and the leak to the Evening Standard in London comes at an embarrassing time as minis ters determine how hard they should stamp on smoking in the long-promised public health white paper next month.
The Scoth review of the evidence on passive smoking suggests there is about 25% increased risk of lung cancer and of heart disease in non-smokers if they are exposed to other people's smoke. New studies had also confirmed health damage in infancy and childhood.
The Department of Health tried to fend off suggestions it had sat on the report.
"The vast majority of the studies on second-hand smoke look at the effects of non-smokers living with smokers," said a spokeswoman. "Ministers have been looking for evidence around the impact of second-hand smoke in public places. not simply private homes."
She added the government had launched a campaign depicting the danger of smoking around babies and children.
However, Andrew Lansley, for the Conservatives, said there needed to be a consistent message about the dangers of smoking. "On the one hand, the report suggests a ban on smoking in public places, whereas on the other [health secretary] John Reid tells an audience that for some people smoking is one of life's small pleasures."
Paul Burstow, for the Liberal Democrats, said: "Ministers should introduce a ban on smoking in enclosed public places to protect people working in bars and restaurants from the effects of second-hand smoke. This was recommended by their own chief medical officer last year. A ban should be on a national basis and not a piecemeal ban which only takes in certain parts of the country."
Doctors weighed in, too. John Britton, chair of the Royal College of Physicians' tobacco advisory group, said there could now "be no excuse for not introducing a total ban on smoking in enclosed spaces as soon as possible."
Brendan Barber, general secretary of the TUC, said: "Workplaces will be safer when they are smoke-free. Half-measures will not save the 700 employees who die every year due to passive smoking at work."
Deborah Arnott, director of anti-smoking group Ash, said that it was "deeply worrying" that the government should have sat on the report when it should have been published in good time to inform debate on the white paper. "Remarkably, on TV yesterday, Mr Reid was still referring to the 'possible' health effects of second-hand smoke."
But Simon Clark, of the smokers' lobby group Forest, said that the report sounded "dubious". He added: "It is simply not true that the vast majority of research shows passive smoking is damaging health. There have been almost 150 studies on passive smoking and overall the resulted are inconclusive."