Research published online in Tobacco Control says that UK children are being exposed to millions of tobacco images every week on prime time television.
Smoking and other tobacco content frequently feature in films marketed to kids, which is known to spark their interest in starting to smoke, say the authors.
More stringent curbs on tobacco imagery in the TV programme schedule could help curb uptake among young people, who spend an average of 2.5 hours in front of the box every day, they suggest.
The content was then coded in 1 minute intervals according to whether it was: actual use of a tobacco product; implied use; the presence of tobacco paraphernalia, such as packs and ashtrays; and other references to tobacco, such as a news report.
The authors also looked for appearances of clear and unambiguous tobacco branding and merchandising.
In all, the 420 hours of recordings comprised 613 programmes plus 1121 adverts and trailers, totalling 25,210 part or full minute intervals. Documentaries (161), news programmes (139), and soap operas (72) were the most common genres.
Among the 613 programmes broadcast, a third (210; 34%) contained some tobacco content. This occurred at least once in more than half of all reality TV (67%), feature films (64%), and comedy (52%) programmes, and in around half of soap operas (49%) and dramas (48%).
Over two thirds of tobacco content (69%) featured in the 75% of hours of programmes in the sample broadcast before the 9 pm "watershed" which marks the line between material more suitable for adults than for children.
The break-down of content type showed that actual tobacco use occurred in 245 (1%) of all 1-minute intervals, in 73 (12%) of all programmes, and (0.7%) of all adverts/trailers.
At least one appearance of implied tobacco use, tobacco paraphernalia, or other references to tobacco occurred in 618 (2.5%) 1 minute intervals. And 66 tobacco branding appearances occurred in 27 1 minute intervals in 18 programmes.
Based on the programme content and the sizeable audience viewing figures for young people, this translates into 59 million instances of tobacco imagery/messaging, 16 million of actual tobacco use, and 3 million of tobacco brand appearances every week, say the authors.
Tobacco advertising, sponsorship and promotion in TV programmes are banned in the UK, but imagery included for artistic or editorial reasons is exempt.
Nevertheless, the appearance of real brands in fictional programmes, such as soap operas, is "of questionable legality," comment the authors, who call for the regulations and guidelines on tobacco content to be reviewed, to protect children.
"We would recommend that future television programming remove gratuitous depictions of tobacco, particularly actual smoking and tobacco branding, from programmes aimed at young people, or, in the UK, scheduled before the 2100 watershed," they write.