Films that depict actors smoking should be handed an automatic 18 certificate, according to research published by the Thorax, a medical journal co-owned by the British Thoracic Society.

The report, produced by researchers from the UK Centre for Tobacco Control Studies, called for movies that feature smoking to attract a similar age classification to those that portray sex or violence. Their study of more than 5,000 adolescents found that 15-year-olds who saw the most films showing actors smoking were 73% more likely to have tried it than those who had seen the fewest.

Dr Andrea Waylen, from the University of Bristol's school of oral and dental sciences, said: "More than half the films shown in the UK that contain smoking are rated 15 or below, so children and young teenagers are clearly exposed.

"Our results confirm an association between this exposure and youth smoking in this country, indicating that raising the certification to 18 in the UK is likely to lower smoking rates among youth.

"Given that smoking depictions in films are not consistent with the ban on smoking in public places in the UK and that the relationship may be causal, a precautionary principle should be pursued. Films ought to be rated by exposure to smoking in the same way that they are currently rated by level of violence."

Respondents to the survey were asked whether they had seen 50 films randomly selected from 366 box-office hits between 2001 and 2005, including Spider-Man, Bridget Jones and The Matrix. Those who had seen the most films in which smoking was shown on screen were almost 50% more likely to be a smoker than those who had seen the least.

Smoking in movies has often been associated with glamour, particularly in the early years of Hollywood when actors such as Audrey Hepburn were regularly seen puffing on a cigarette in films such as Breakfast at Tiffany's. Despite changes in attitudes towards smoking in subsequent decades and stringent calls from campaigners for new guidelines, film-makers remain free to portray the habit on screen without fear of censorship.

In response to the latest report, the British Board of Film Classification said its current guidelines were "proportionate; take due account of the available evidence of harm; and reflect the clear wishes of the public".

Director David Cooke said: "Glamorising smoking has been included as a classification issue in our published classification guidelines. There is, however, no public support for automatically classifying, for instance, a PG film at 18 just because it happens to contain a scene of smoking."

Five films that children might be banned from viewing if smoking attracted an 18 certificate

The Lord of the Rings trilogy (2001-2003)

Gandalf the wizard has a huge fondness for smoking tobacco through a pipe in Peter Jackson's fantasy trilogy based on the novels by JRR Tolkien (himself a keen smoker). Hobbits Pippin and Merry also enjoy a puff of the Shire's finest pipe-weed.

101 Dalmations (1996)

Glenn Close's Cruella DeVille (via a sleek 20s-style cigarette holder called a quellazaire) is rarely seen without a fag poking from her lips.

Peter Pan (1953)

Captain Hook takes his smoking habit to extremes in Disney's animated tale, via a holder that allows him to inhale from two cigars at once.

Alice in Wonderland (1951)

The walrus smokes cigars, the dodo enjoys a pipe, and the caterpillar loves to puff on a hookah in the Disney classic.

Pinocchio (1940)

Two ruffians do their best to convince the innocent puppet to take up smoking in Disney's animated retelling of the Carlo Collodi fairytale.

• This article was amended on Wednesday September 21 2011. We said that the research mentioned in the article above had been published by the British Medical Journal. In fact, the research was published in Thorax, a journal produced by the BMJ Group and co-owned by the British Thoracic Society. This has been corrected.