HBOS will now get the money it needs from its underwriters
Rumours of a funding crisis at Halifax Bank of Scotland (HBOS) hurt its share price, but it was difficult to measure the impact, the City watchdog has said.
The Financial Services Authority (FSA) said turbulence in the market may also have played a part in the bank's shares tumbling nearly 20% on 19 March.
An FSA probe found no evidence that rumours were spread in a "concerted attempt" by individuals to profit.
HBOS later raised £4bn in a rights issue, but largely from underwriters.
HBOS shares had begun to fall from about 0830 on 19 March, accelerating until an automated trading halt was hit - before sinking dramatically when trading resumed.
However they ended the day just 7% lower than the previous day.
"There is no doubt that false and damaging rumours were circulating about HBOS.... and these would have had some impact on HBOS' share price," the report said.
"It is difficult, however, to say how much impact, as the share price was also affected by the interaction of a number of other complex factors on the day."
It added: "Despite the likelihood that the rumours contributed to the fall in the share price, the FSA has not uncovered evidence that they were spread as part of a concerted attempt by individuals to profit by manipulating the share price."
The watchdog said that it was looking at how to deal with market rumours, including examining how rumours are verified, and whether traders can pass on or trade on information being spread.
When HBOS launched its rights issue in April, its shares cost about 500p.
Shareholders were offered two new shares at the then heavily-discounted price of 275p for every five shares they already owned.
Since then, housing market concerns and fears about further write-downs in the banking sector have weighed heavily on shares.
Investors overwhelmingly declined the chance to buy new shares in the firm - because they were available on the stock market for less than the issue price - making it unattractive to shareholders.