The BBC Trust has provisional approved plans to launch a free satellite TV service as a joint venture with Channel 4 and ITV.

BBC channels are currently available for free through Sky's Freesat service, which requires a set-top box and one time installation that costs £150.

"Overall, we believe a 'Freesat' service to be in the public interest and we hope that other public service broadcasters would join the BBC in a joint venture", said the Trust's announcement.

The Trust has admitted that its proposed Freesat service would like create greater competition for Freesat from Sky, and may even have an impact on subscription services.

One advantage the Freesat would have over Freeview is that it could support more high-definition channels than Freeview can.

It would also be available in the 27% of the country that can't receive Freeview because of reception problems with the digital signal.