FM radio should be switched off by 2017, forcing listeners to buy digital sets, a Government-backed body of industry experts is expected to conclude today.

The Digital Radio Working Group, chaired by Barry Cox, a former deputy chairman of Channel 4, said that Radio 1, Classic FM and all other national stations as well as big local stations could be forced on to digital only when three conditions are met.

No switchover from FM should take place until 50 per cent of radio listening is through DAB digital sets, so only a minority of households would be forced to upgrade the 150 million analogue sets in existence. Digital radio listening accounts for 18.7 per cent of the total, according to the most recent data.

Mr Cox said: “Most importantly we need to see overall coverage for DAB improve, along with more focus to get motorists to adopt DAB so that it can be a real alternative to FM services”, he said.

DAB has so much ground to gain that a switchover is not expected until between 2015 and 2020, with the working group picking 2017 as a likely date. That is several years later than Ofcom had previously indicated: Ed Richards, the regulator's chief executive, suggested a year ago that the FM switchoff could begin in 2012.

Digital radio remains a minority choice partly because of the cost of the sets. More than eight million have been sold in the UK and it is expected that about 1 million will be sold over the Christmas period.

However, only three in ten homes have at least one digital radio set.

The other conditions for digital migration require DAB signal strength and range to match that of FM, which covers over 90 per cent of the UK.

Mr Cox’s group believes that the BBC and commercial radio owners will need two years to prepare for the switch, implying that 2017 is the most likely first possible date for the change, five years after the transition to digital televisoin will have been completed.

In return for agreeing to the change, all FM stations will be allowed to keep their licences until 2017, meaning that any licence renewals that are due to take place before the switch will be scrapped.

However, small community radio stations will be allowed to continue to use FM, because of the greater expense of running a digital service and a shortage of capacity, giving existing tuners some use in the decade after next.

Andy Burnham, the Culture Secretary, said that he was "pleased that the working group has been able to achieve such consensus."

He said that the Government would study the group's recommendations carefully. The document will become part of Lord Carter’s Digital Britain green paper, with Mr Cox joining his advisory panel. The paper is expected to be published at the end of January.

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