Ofcom has confirmed that viewers will be able to watch high-definition TV on Freeview from 2009, with three new HD channels due for launch next year and a fourth in 2012.

The channels will be available through ordinary aerials without a subscription, but viewers will require a HD-ready TV set and a new set-top box.

Viewers will also have to wait until analogue TV is switched off in their area, which means it will be 2012 before regions including London, the north-east of England and Northern Ireland can receive the new channels.

The BBC looks set to keep one of the channels with the remainder heading for auction to the commercial networks ITV, Channel 4, Five and the Welsh network S4C.

"This is a once-in-a-lifetime opportunity to upgrade digital terrestrial television," said Ofcom chief executive Ed Richards.

"It offers benefits for broadcasters, which will be able to launch new services without using any new spectrum, and viewers, who will have access to new channels and services on free to air."

The move is widely seen as a blow to Sky television, which currently provides the vast majority of HD TV channels through a £249 set-top box and a minimum £26 per month subscription.

Virgin Media's cable service offers a minimal number of HD TV channels, while free satellite TV service Freesat is due to launch later this year.