B&B shares opened strongly, rising 5bp to 33p on speculation that the City watchdog the Financial Services Authority was seeking a buyer.
But it was later countered by fears that no such white knight would emerge, and the bank ended the day up only dp at 28bp.
It emerged that banks approached by the FSA were ruling themselves out, while it is believed B&B is not in any takeover talks.
Possible buyers included Abbey and Alliance & Leicester owner Santander, Clydesdale-owner National Australia Bank and ING, which runs ING Direct.
Entrepreneur Clive Cowdery’s Resolution Group, whose takeover attempt was rebuffed earlier this year, remains a possibility.
Analysts take a gloomy view of B&B’s prospects, however. JP Morgan said it was “not a viable standalone entity”, while Panmure Gordon said a buyer would have emerged by now.
It cut B&B’s share-price target from 20p to 7p.