The source said: "These are very bad numbers for GCap, particularly given the ongoing continued poor performance of its London stations and these results won't help the company persuade the shareholders that the management has its hand on the tiller.
"This would add further pressure on GCap when it delivers its defence document."
This refers to newly appointed chief executive Fru Hazlitt's forthcoming presentation to shareholders, scheduled for February 11. GCap's shareholders are understood to be waiting to hear her strategy, while Global is biding its time before coming back with a fresh bid.
In the Rajar fourth quarter 2007 figures, published yesterday, GCap's total listening hours were 130,862, down 9% on last year and 4% on the third quarter of 2007.
The remarks are a veiled criticism of Hazlitt's record as managing director of GCap's London stations -- the role in which she joined GCap seven months ago, before her promotion to chief executive in December.
In London, GCap had a severe problem with its Gold station, which lost almost half of its 426,000 listeners in one quarter.
Capital Radio's reach dipped by 11% from the third quarter to 1.7m, but its share of listening held up at 4.7%, equal to its best performance during the past year.
Dance station Choice was hit by a downturn in listening share, from 2% in the third quarter to 1.7%, and a big drop in reach from 611,000 to 485,000.
Indie station Xfm grew its share from 1.2% to 1.3%, although its audience dropped 7% to 513,000.
A GCap spokeswoman refused to comment on Global's criticism, because it was not from a named source.
GCap yesterday secured the takeover panel's intervention in the battle with Global, with the market regulator ruling that Global must come back with a new bid by 5pm on March 5 or walk away for six months.
Global has so far made one bid at 190p per share, proposed to GCap in mid-December. It was turned down without the knowledge of GCap's shareholders.
GCap's shares went on to hit a high of 210p on January 8 and have gradually fallen back this month. They were trading at 186.5p this morning.
GCap yesterday revealed its fourth quarter revenues were up 4% year on year, "broadly in line with the market", according to its spokeswoman. The market growth figures could not be confirmed at the time of writing.
Two other radio groups put the market's growth at 7%, and while the Global source was unwilling to reveal its growth figure they claimed it was better than GCap's.