Radio 1's breakfast show lost 264,000 listeners in the second quarter of this year, it said, bringing its total weekly audience down to 4.5 million.
The figures are a blow for BBC radio bosses whose mission is to halt the collapse of the Radio 1 audience from 21 per cent of all listening five years ago to 9.5 per cent now.
It is particularly worrying for the BBC that commercial radio is taking 65 per cent of listening among 15-44-year-olds and, with 51 per cent of total listening, commercial radio has recorded its highest share yet.
"We think the main problem with the breakfast show is that people are getting up later," said a BBC spokeswoman in an effort to explain the exodus of listeners from Ball's programme.
She pointed out that Simon Mayo's show, starting at 9am, had augmented its audience by nearly 250,000.
At rival Virgin, this was dismissed as a "daft excuse", and other industry insiders were also less than kind, saying that a question-mark must hang over the performance of Ball in the early-morning slot.
Capital Radio's Chris Tarrant was another loser in the hard-fought battle of the breakfast shows.
His audience fell by 11 per cent to 1.8 million - but Capital was keen to emphasise that the old man of pop still outperforms Virgin's Chris Evans in London, with an audience three times the size of Virgin's breakfast programme.
The Chris Evans show, countrywide, was the only big player to show an increase, with a 2.5 per-cent rise, to reach a weekly audience of 2.5 million.
Over the year, Evans has increased the Virgin breakfast audience by a 639,000 listeners, and a spokesman described his programme as forging ahead while his rivals were in decline.
In one sense, the biggest success at breakfast time was Talk Radio's Kirsty Young. Although the Channel 5 news presenter is a minnow among the breakfast-show hosts, she secured a 4 per cent rise in her audience to 864,000.
Paul Robinson, the managing director of Talk Radio, said Young had been the only presenter in the firmament to build her audience sharply with each set of figures, and he expected her listenership to rise to 1 million by Christmas.
Talk Radio as a whole is experiencing something of a renaissance, and this quarter achieved its highest audience yet at 2.6 million - a figure that must be music to the ears of the former Sun editor, Kelvin Mackenzie, who is putting together a takeover package for the station.
The National Dawn Chorus
ZOE BALL: RADIO 1
Daughter of Seventies children's television presenter Johnny Ball, she was recruited after the failure of Mark Radcliffe to give breakfast- time Radio 1 a popular touch following the departure of Chris Evans. She also gives it a blonde presence in the tabloids. While the rest of Radio 1 plays newer, hipper music, the breakfast show still needs to bring in a big audience to get listeners tuned to the station for the rest of the day. Ball came from children's television and needs her partner Kevin Greening to manage the programme musically.
CHRIS EVANS: VIRGIN
The human PR machine won a special Sony Radio Award this year specifically for raising radio's profile. Broadcasting style is not revolutionary but he can make people laugh without thinking. Much of his life in the headlines gets into the show, giving listeners a vicarious taste of the celebrity lifestyle. Has seen off the national competition from Radio 1, and is now targeting Chris Tarrant's London dominance. When the veteran Capital DJ moved his start from 6.30am to 6am last week, Evans moved from 7am to 6.30am. Bought Virgin last year for pounds 65m.
CHRIS TARRANT: CAPITAL
Old enough to be Evans's father, but views the younger, brasher man as his biggest rival. Remembered by thirtysomethings as presenter of the legendary Tiswas programme, Tarrant has since become a rich man. In 1996, he turned down an offer from Richard Branson to join Virgin for pounds 1.2m, and now has a three-year contract with Capital worth pounds 3m. In his spare time he has built up a clothing company in Italy valued around pounds 20m. Like Evans, he likes to present himself as a bad boy, and claims he drank a swimming pool of whisky when his daughter was born.
KIRSTY YOUNG: TALK RADIO
Her mission was to make Talk Radio glamorous and help it shed its shock- jock image. She shot to stardom as the main presenter of Channel 5 news. With a Vogue photoshoot and winning performance on Have I Got News for You, she has hit the big time. Four years ago, she earned pounds 40,000 as a Scottish Television presenter; Channel 5 and Talk Radio are said to pay her pounds 750,000. She is still working at the lower-audience end of the market, though - and at Talk Radio cannot attract the big listenership of the rival pop-music breakfast shows.Reuse content