Britain's publicly-funded BBC could be forced to share its licence fee and commercial rival ITV could drop its public service remit under proposals aimed at helping broadcasters adapt for the digital age.

Broadcasting is heavily regulated in Britain and the main terrestrial providers such as ITV, the BBC and Channel 4 are expected to produce a certain amount of programming such as children's TV and regional news in exchange for spectrum.

But the commercial broadcasters and analysts have long argued that with viewers and advertisers moving to multichannel TV and the Internet, such requirements are expensive and prevent the broadcasters from competing fairly.

Media regulator Ofcom has been looking at the issue and on Thursday outlined some possible options to tackle the problem. It believes a new model will be needed by 2011.

"Public service broadcasting is at a crossroads," said Ofcom Chief Executive Ed Richards in a statement. "Viewers still want a mix of high quality UK-made content, but the traditional television model is not enough to meet all their needs.

"Today's proposals outline options for a securely-funded PSB future. Now is the time for a wide-ranging debate looking carefully and dispassionately at all the options."

The four possible models included: allowing the BBC, ITV1, Channel 4 and Five to provide public service programming as they do now but with either extra public funding or fewer obligations for the commercial channels.

Asking only the BBC to provide such programming, asking only the BBC and Channel 4 to provide public service programming with limited competition from others which bid for long-term funding, or asking a wider range of providers to bid for long-term funding to provide competition to the BBC.

Funding for these new models could either come from the government or the licence fee - a tax on all UK television-owning households.

But any decision to share the licence fee could prove unpopular with Britons who strongly regard the corporation and would not wish to see a drop in standards.

Ofcom said its initial consultation showed that audiences valued competition for the BBC, but the underlying economics of commercial public service broadcasting were difficult.

Ofcom research showed that audiences wanted content that reflected life in the UK and its cultural identity while increasing understanding of the world, stimulating knowledge and raising awareness of different cultures and viewpoints.

Both Channel 4, which is publicly owned but funded by advertising, and ITV welcomed the proposals. The BBC said it would launch a wide-ranging debate with the public and the creative community before responding to Ofcom's review.

"Ofcom's first-stage report raises some important issues which require serious consideration and open debate," said Michael Lyons, Chairman of the BBC Trust.

"The Trust will listen to a wide range of opinion as we consider our response, and we will place special emphasis on the views of the wider public."

The regulator said it would consult a range of opinions as part of its review which ends on June 19. It will then hold a second consultation later in the year to examine the possible long term models.

Any final decisions for substantial change in the way PSB is provided or funded will be for the government and parliament.