The BBC is expected to launch a high definition TV channel later this year after getting the green light from media regulator Ofcom and the BBC Trust.

The format promises pictures four times sharper than standard broadcasts, with programmes such as Planet Earth and Bleak House already made in this way. It has been recommended that the channel is aired between 3pm and midnight every day.

The new channel would also be available on FreeSat – the free to air satellite service due to be launched next year. A cut down version would also be shown on Freeview.

Ofcom concluded the move would have little impact on commercial rivals. However the watchdog also warned that the new channel should offer a range of programmes, rather than just one genre.