The four main broadcasters in Britain, including the BBC and ITV have agreed to put high-definition channels on the Freeview platform in time for the 2012 digital switchover. 

All four channels have been calling on the media regulator Ofcom and the government to reserve some of the spectrum that will be freed up from the switchover from analogue to prevent a national "HD Divide".

But any broadcaster will face competition from wealthy telecoms groups, among others, as Ofcom says it intends to conduct an auction.

The transition to HDTV has been called a landmark move for the industry, similar to the shift from black-and-white to colour, and the broadcasters want to be able to compete with the sharply improved TV picture offered by pay-TV firms BSkyB and Virgin Media.

Under the agreement, the BBC will set aside one of its two multiplexes to carry HD services from the BBC, ITV, Channel 4 and Channel 5.

Through the use of new technologies, it hopes to increase the capacity on the popular service and should not need to drop any channels.

BBC, ITV and Channel 4 HD services could be on the platform from 2009 or 2010, with Five HD launching by 2012 at the latest.

Freeview is currently in 14 million homes in the UK, making it the most popular digital TV service in Britain.