Channel 4 and Discovery are among four broadcasters reprimanded by the advertising regulator ASA for screening alcohol adverts during programmes aimed at under-18s.
Paramount and Entertainment Networks were also handed warnings after alcohol adverts were shown during programmes such as Stuart Little 3: Call of the Wild, which was transmitted at 3.30pm.
UK broadcast advertising rules state that alcohol ads should not be shown in or around programmes commissioned for, principally targeted at or likely to appeal particularly to audiences below the age of 18 years.
The Advertising Standards Authority (ASA) made three separate rulings that Channel 4 broke scheduling restrictions for screening alcohol ads around the programmes The Big Bang Theory and How I Met Your Mother and the film Aquamarine, about two teenage girls and a mermaid.
The code advises broadcasters to use an audience indexing tool to determine how many children are watching, stating that an alcohol restriction should be applied when the number of 10 to 15-year-olds watching are 20 per cent over-represented in the programme audience compared to the audience as a whole.
Data highlighted that the audience index for alcohol advertisements exceeded the 120 limit in 28 episodes of The Big Bang Theory, which Channel 4 said had been regularly scheduled at 8pm on E4 since November 2011.
E4 said they monitored the programme and provided a table showing that the monthly average index did not exceed 120 at any point in the first six months.
They said their standard procedure was to review the series on a quarterly basis and respond to any audience changes. However, this process was “unfortunately” not followed on this occasion so they were unable to respond accordingly to the change in the audience demographic.
Channel 4's Film 4 agreed that the film Aquamarine was principally directed at audiences aged under-18, but the alcohol restriction was not applied on one occasion “due to an error”.
The ASA issued a warning to Discovery for showing alcohol ads during the Mythbusters science series, rejecting the channel's argument that the programme was directed at over-18s.
It also reprimanded Entertainment Networks parent company Sony Pictures for showing such ads during films including Jungle Boy and Fly Away Home, which the company agreed were directed at under-18 audiences.
A Channel 4 spokeswoman said: “We accept the ASA's findings of the three incidences. We are currently putting in place additional safeguards against such occurrences in the future.”
Additional reporting by PA