One in six of all viewers of Skins, the Channel 4 sixth-form drama, is watching the late-night programme via the internet, as young audiences abandon the television set to catch the show.

The first episode of the third series, which was broadcast on the E4 digital network on January 22, was watched by 1.35 million on television and by 283,000 via a website - meaning that 17.3 per cent of the programme's viewing took place online.

Channel 4 believes that the high proportion, repeated for the second episode, reflects a clear sign of how quickly viewing habits are changing among younger viewers. More than half of Skins watchers are under the age of 34.

Jon Gisby, Channel 4's director of future media, said: “This is an audience of people like students that have access to broadband, computers and wi-fi, but do not tend to have access to pay-television and personal video recorders.

“Doubtless they will watch more conventional television as they get older, but we should not underestimate the degree that these habits will stick.”

Skins, with its young cast, whose ranks have included Dev Patel, the Slumdog Millionaire star, is unusually popular online. The proportion of computer viewing is usually much smaller for other programmes, at well under 5 per cent.

But all main broadcasters have been surprised by the public's willingness to abandon what used to be considered the small screen in favour of even smaller displays provided by computers.

Simon Nelson, the controller of new media for BBC television, said that during December, viewers watched programmes via the corporation's iPlayer a record 41million times. “I don't think any of us expected the rate of growth we are now seeing in online viewing,” he said.

Programmes with a similar demographic profile to Skins are particularly popular for online viewing on BBC sites, although the corporation will not release precise figures.

Among the programmes highlighted by Mr Nelson were Doctor Who, Top Gear, and Being Human, a BBC Three comedy-drama about three flatmates who take the form of a ghost, werewolf and a vampire.

However, the problem for commercial broadcasters is that it is proving more difficult to sell adverts online, where, for example, Channel 4 screens just three minutes of advertising in a 60-minute programme such as Skins. On digital television it is able to show an average of nine minutes an hour.

Mr Gisby said that online viewers were less keen on advertising, and as a result, online viewers were potentially worth less to commercial broadcasters. “Over the long term, we will have to become more innovative because as more people tune in online it will become more and more challenging commercially,” he said, echoing Channel 4's fears that its long-term economics are under pressure.

Other commercial internet broadcasters believe it is possible to screen more advertising - and that it is possible to find other ways of getting viewers to watch commercials. Joost, an internet television service where old episodes of Peep Show, the comedy, and He-Man, the cartoon, can be found, screens five minutes of advertising an hour.

Henrik Werdelin, chief creative officer of Joost, said that “we are not being inundanted with complaints” over the advertising levels, and said that by using targeted advertising it was possible to achieve a revenue per thousand viewers of between £7 and £40 - comparable to broadcast television in the UK.

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