Britain's digital TV experts have put forward a plan to dramatically expand hi-def TV on Freeview and safeguard the service for more than a decade.

The Advanced Digital Television Services plan was proposed to the Digital TV Group Summit by four of the group's top engineers.

It builds on Ofcom's proposal to launch a single Freeview multiplex for hi-def channels in 2009, using new technologies of MPEG-4 compression and DVB-T2 transmission.

The DTG's Dr Ian Childs described the plan as 'Digital Television 4.0', and said it could add up to extra eight national HD channels from 2012, and pilot TV for portable sets and mobile viewing in time for the 2012 Olympics.

He said: "Flat panel HDTVs have been flying off the shelves by the millions. Unless major action is taken now, the full benefit of these advanced technologies could be missed and the majority of UK households could be saddled with a second class digital television service.

"There is now the opportunity to create a truly world class free-to-air advanced digital television service, maintaining the UK's position as a leader in television production and broadcasting and providing a highly compelling service to consumers."

But the real benefit would be realised by the end of the next decade, allowing Freeview to carry up to 40 hi-def channels on fewer frequencies.

There would also be a pilot scheme for national portable and mobile TV, using DVB-H and MIMO technology to create a super-robust signal.

To achieve the plan, Ofcom would have to have to set aside old analogue TV space for two new national digital TV networks on a single frequency - also known as Single Frequency Networks.

These would be used to juggle Freeview channels around through the decade, gradually moving to a highly efficient system with more channels than the current Freeview lineup, and all using both DVB-T2 and MPEG-4.

Ofcom would eventually be able to sell off even more spectrum than in the current Digital Dividend auction, possibly raising more money for the Treasury.

Dr Childs added that he hoped the industry, government and regulators could take the proposal as a starting point to plan digital TV after 2012.