Chris Moyles is taking over the Radio 1 Breakfast Show

The BBC currently accounts for half of all radio listeners - but director of radio Jenny Abramsky said she expected its audience share to fall by 2010.

Nevertheless extra digital stations were "the right strategy", she told the National Association of Broadcasters.

"If radio were the only medium not to go digital it would soon become obsolete for future generations," she said.

Ms Abramsky welcomed the increased choice from digital radio as "fantastic news" for listeners and the industry, even though it would inevitably lead to a decline in the share of listening to BBC Radio.

"We expect our share of listening will fall, but increased choice is the right strategy because we know that is right for audiences - it is what sells sets and is what will take radio digital," she said.

New age

The BBC launched a range of digital-only stations last year, including black music station 1xtra, 6 Music and comedy and drama channel BBC 7.

The first digital listener figures will be available later this week, although Abramsky said these would be "modest" because it was "early days".

BBC Radio 2 is currently the most listened-to station in the UK, with 13 million listeners.

BBC Radio 1 recently announced it was replacing breakfast show presenter Sara Cox with Chris Moyles, after a decline in ratings.

The station saw its weekly audience figures fell below 10 million between April and July this year, losing almost 500,000 during the three-month period.

Ms Abramsky's speech was read by the BBC's controller of radio and music new media, Simon Nelson, to the National Association of Broadcasters on Monday.