FOUR broadcasters including Channel 4 and Discovery have been reprimanded by the advertising regulator for showing alcohol adverts during programmes aimed at under-18s.

Paramount and Entertainment Networks have also received warnings after alcohol ads screened during programmes such as Stuart Little 3: Call of the Wild, an animated film about a mouse which was transmitted as early as 3.30pm.

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.

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 code recommends that broadcasters use a tool called audience indexing 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% over-represented in the programme audience compared to the audience as a whole.

Data found that the audience index for alcohol ads 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 usual process was to review the series on a quarterly basis and act upon any audience changes, but this was "unfortunately" not followed on this occasion so they were unable to respond to the change in the audience profile.

Channel 4's Film 4 agreed that the film Aquamarine was principally directed at under-18 audiences, 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."