ITV1, Channel 4 and Five could be allowed to show 12 minutes of advertising every hour between 6pm and 11pm nightly, in a move that could be worth up to £120 million to the under pressure commercial broadcasters.

Current rules limit ITV1, Channel 4 and Five to showing an average of 8 minutes an hour of advertising in peaktime — but today Ofcom, the communications regulator, suggested that the rule could be relaxed.

That would allow ITV1 to air 60 minutes of adverts between 6pm and 11pm, on a Saturday night when the broadcaster is scheduling the X-Factor and I’m A Celebrity...Get Me Out Of Here.

ITV1 and the other broadcasters, though, would still be subject to a separate rule which means that no more than 12 minutes of advertising can be shown in any one single hour — meaning that the extra ad breaks would have to be spread evenly through the night.

The extra adverts would come even though Ofcom’s own research into viewer behaviour shows that the public does not want to see more advertising, a conclusion supported by advertisers who don’t want their messages cluttered by rivals.

“We want to support investment in good quality programming, but we don’t want advertising to be intrusive,” said Stuart Purvis, a partner for content and standards at Ofcom. Ofcom’s figures estimate that for every extra minute added to the average would add £30 million in revenue to ITV, Channel 4 and the RTL-owned Five.

To keep viewers happy, Ofcom indicated it was wanted to maintain the overall daily limit of advertising. Across the day, ITV1, Channel 4 and Five, are allowed to schedule an average of seven minutes of adverts per hour, and Ofcom said yesterday it was minded to leave that limit unchanged.

In practice, the three broadcasters reduce adverts in the daytime, and increase them at peak time - which means that between 7pm and 10 pm they can air close to 12 minutes an hour. But because of the separate peaktime limit, they show far fewer adverts during News at Ten, and other serious programming.