The Government is going ahead with plans for digital radio but no date has been set for the switchover, Communications Minister Ed Vaizey is due to announce.

Although a provisional target of 2015 was suggested by the former Labour government, Mr Vaizey will say that "the weight of public opinion" will decide when the FM signal should be switched off.

He will say that when half of all radio listeners have switched to using digital sources the Government will make a decision.

For many drivers it will mean the prospect of buying new radios or using conversion kits as digital radios are not often fitted as standard.

Figures from radio industry audience body Rajar show that around 24% is currently via digital.

Mr Vaizey is to publish a Digital Radio Action Plan encouraging listeners to make the switch.

This will involve building DAB coverage, which only covers about 90% of the population, and a cost-benefit analysis of the changeover.

Speaking at the Intellect Digital Home Conference, Mr Vaizey will say: "Listeners need to be persuaded that the content on offer is compelling, that the quality is high and that digital radios, at home or in the car, are affordable and have listening quality that is at least as good as FM."

Michelle Mitchell, Charity Director at Age UK, said: "Age UK welcomes today's announcement of the Government's Digital Action Plan for the switchover of radio from analogue to digital.

"Many people in later life have multiple radios and replacing them all could be expensive, especially for those on a limited budget. Therefore a cost benefit analysis must be produced to clearly demonstrate the benefits to listeners of moving to digital.

"Age UK also believe there is a need for a Help Scheme, similar to the digital TV switchover Help Scheme, which will provide specific help, information and advice on the switchover to those who need it mos