A switch-off date for analogue radio will be decided later this year by Culture Secretary Tessa Jowell.
Digital radio growth is happening quickly in Britain
Ms Jowell said she would review digital radio take-up in a foreword to a report due to be published by the industry's Digital Radio Development Bureau.
She said she would be "considering how long it would be appropriate for sound digital broadcasting services to be provided in analogue form".
By the end of June, 600,000 digital radios had been sold in the UK.
The decision to switch off analogue radio will mean about 100 million radios will become obsolete.
There was a 444% annual growth in the take-up of DAB digital radios last year in the UK, second only to the MP3 player in the consumer electronics market.
Digital radios priced at £50 will be available at supermarkets later this year.
But while many existing stations and other new services have signed up for the new digital networks, other stations have yet to make the move.
Some 385 services are already available on a digital signal, representing just under half of the total number of broadcasters.
Digital radios with hard drives to record programmes are already on the market, and most scroll information including track listings and news across a screen on the front of the set.
About 2.2 million people say they have listened to radio through a mobile phone, with 13 million tuning in via the internet.