Here's looking at you, kids: from Humphrey Bogart to Sharon Stone and Colin Farrell, the big screen has been lit up by chain-smoking, hard-drinking stars. Their days may be numbered. By Francis Elliott

Film censors are considering new measures to protect children's health by clamping down on Hollywood scenes of drinking and smoking, The Independent on Sunday has learnt.

In future, tobacco and alcohol could be included alongside sex and violence when the film board classifies new movies - a step which could ban children from watching films where heavy smoking is portrayed.

The film industry has become the latest front in the battle over cigarettes. Government proposals enabling local authorities to impose workplace smoking bans, first reported in this newspaper, were backed by Tony Blair last week. Research suggests children are nearly three times as likely to try tobacco if they regularly watch movie actors smoke, with films exerting a more powerful influence than tobacco advertising.

John Reid, the Secretary of State for Health, signalled his personal scepticism over the plans, however, when he said that smoking had become a "middle-class obsession". And those fearing the resurgence of a nanny state will be dismayed to learn that the habit faces the censor's blade.

The British Board of Film Classification has included smoking and drinking in a list of activities that could be covered in new guidelines for age restrictions that will come into force later this year. A final decision on whether films that include smoking will be rated at 15-plus is expected within the next few months following a consultation exercise.

British cinema-goers have been asked whether they believe smoking and drinking should fall under the censor's axe. The BBFC said it was reviewing its classification guidelines earlier this year. Robin Duval, the board director said, it wanted to check public views on bad language, sex and violence in films.

However, the body later quietly added a number of other issues, including smoking and drinking, before starting the exercise in which 10,000 people have been asked for their views. Among the questions asked is whether only the "hero" of a film should be seen smoking or whether no smoking should be shown at all.

The initiative has received a mixed response from film critics, who raised the possibility of "anachronistic film- making" where scenes set in the 1940s or 50s would show no one smoking. Will Self, the Evening Standard's film critic, said: "In LA Confidential, which is a good film, there's one scene set in a 1950s Los Angeles police squad room, and no one is smoking. Already films are becoming anachronistic in their treatment - you get working-class pubs where no one smokes."

The film critic Barry Norman, said: "It would be the most unbelievable piece of censorship. At the moment Bruce Willis is the only leading man I can think of who smokes on screen. The only other people who smoke cigarettes are villains - that's how you know they are the villain, when they light up."

But the Oscar-winning film producer Lord Puttnam was delighted with the BBFC's proposals. "As a lifetime non- smoker and somebody who has lost family members to smoking-related illnesses I think it is all to the good," he said. "When I was at Columbia, I stopped scenes showing people snorting cocaine in two films. I have never regretted it."

The BBFC is also consulting on whether "racial or religious references which might be offensive to some people" should be considered by the censors when it comes to rating a film.

Sue Clark, the body's head of communications, said it was too early to say what the results of the survey showed but that they would help frame the new rules. One consequence could be an automatic 18-plus restriction on all cinema alcohol advertisements to protect children from being targeted.

Although the explicit portrayal of smoking in children's films was rare, it did occur, she said, citing Glenn Close's Cruella de Vil in 101 Dalmatians.

Catherine Zeta Jones was criticised for glamorising smoking when she was rarely seen without a cigarette in Chicago, a performance that won her a spoof "Hackademy Award" from the American Lung Foundation.

Dr Vivienne Nathanson, the BMA's Head of Health Policy and Research said: "When smoking is glamorised in movies, young people are encouraged to experiment with a lethal habit. British film stars must be aware that their actions have a real impact on children's lives."

The depiction of smoking on television is covered by an Office of Communications code. It states that its portrayal should be avoided in children's programmes and only included in other material "where context or dramatic veracity requires it". Broadcasters should also take care not to portray smoking as an "attractive activity".

A spokesman for the anti-smoking campaign ASH, which is being consulted by the BBFC, said: "Changing the certificate would be an ultimate sanction, but we want them to think about it. The BBFC is catching up with the tobacco industry, which is very involved in how smoking is portrayed in films. It is a matter of public record that Sylvester Stallone was paid to smoke in Rambo, because the tobacco industry knew that would encourage people to smoke."

A spokesman for Alcohol Concern also welcomed the review, saying: "We certainly have concerns about the way and frequency alcohol is depicted on film and the media in general without balance."

Additional reporting by Andrew Johnson

Can there be fire without smoke?

You can take tobacco out of the movies, but what would actors do with their hands and mouths? Indeed, the fact that there is already much less smoking on film might explain why screen acting is less expressive than in the 40s or 50s, when smoke curled off every star's lip.

Screen smoking provides a whole range of metaphors, and sometimes the downright obvious ones work best. The most famous smoking-as-sex image was in the Bette Davis vehicle Now Voyager (1942), in which the heroine's sexual awakening culminated in leading man Paul Henreid lighting two cigarettes in his mouth, then placing one between her lips. Cigarettes fuelled the sex war in Howard Hawks's His Girl Friday (1940), in which Cary Grant has the effrontery to light his own from Rosalind Russell's lighter. And armies of screen vamps - 20s goddess Louise Brooks, Marlene Dietrich, Veronica Lake - brandished their fags with thrilling insouciance.

Even the way a cigarette was held was convenient shorthand about a character - from the legions of screen Nazis holding theirs between third and fourth finger, to dapper intellectuals like Clifton Webb's Waldo Lydecker in Laura (1944), whose dainty finger-style was implicit Hollywood code for gayness. And sometimes tobacco just meant power. In Sweet Smell of Success, Burt Lancaster's evil gossip columnist did the smoking, but had his minion, played by Tony Curtis, carry the matches: hence the immortal line, "Match me, Sidney". Of all the heavies with chewed-down stogies, the malevolent king was surely Orson Welles's corrupt cop in Touch of Evil (1958), all his badnessin his body seeming to sprout at his mouth in a tuft of rancid weed.

Jonathan Romney