The broadcaster’s plans centre around programming that ties in with its existing content. The strategy begins by emphasising individual programmes rather than a radio station as a whole.

Some of the new material will also be available on Channel 4’s majority-owned digital station Oneword, but the plan is to make all the content available via channel4radio.com. The new medium requires no regulatory approval before it is launched.

Channel 4’s historic move, after 23 years concentrating on television broadcasting, represents the most serious challenge to traditional radio operators, because internet transmission allows new combinations of audio and video.

Andy Duncan, Channel 4’s chief executive, has positioned the move as an attempt to end the BBC’s dominance of radio, although the threat to the commercial sector is just as great. The BBC has a 56 per cent share of listeners, which has been gradually increasing as commercial operators struggle to produce attractive programming.

Mr Duncan, speaking in January, said: “Our aim is to contribute something new to the radio mix by offering a public service alternative to the BBC in news, current affairs, entertainment, lifestyle, music and comedy.”

In a foretaste of the broadcaster’s ambitions, Jon Snow, the newscaster, has been producing a weekly current affairs programme, Snowmail, since October. Broadcast on the digital channel More4 on Saturday evenings, the programme is available on the internet and can be watched or listened to on computer or downloaded on to an MP3 player.

Channel 4 is expected to explore both advertiser funding and subscription models as it seeks to build its overall internet service, although there is little obvious premium radio content that listeners are likely to want to pay for.

Oneword, by contrast, is only forming a modest part of Channel 4’s plans and the speech and music station will not take on the broadcaster’s name. Channel 4 is interested in securing digital radio capacity this year for a cluster of national stations.

Ofcom, the communications regulator, is due to hold a beauty contest for a second block of commercial digital radio frequencies, known as a multiplex. The first commercial block is held by Gcap Media and carries the company’s Classic FM station as well as SMG’s Virgin Radio and UTV’s talkSPORT. The second block is big enough for about eight new national stations and Mr Duncan is hoping to lead a consortium that will win the licence. Ofcom is hoping that only one bidder will emerge for the licence, and is trying to encourage a grand coalition of the commercial radio groups.

Channel 4 has held productive discussions with Emap about a joint bid, but Chrysalis, the third-biggest commercial radio group, is not impressed by Channel 4’s efforts to muscle in and dominate a sector that it has only just entered, leaving open the possibility of a competition for the multiplex. This could leave Channel 4 with nothing.

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