Online travel firm Lastminute.com is to ask the Financial Services Authority (FSA) to investigate an anonymous fax questioning its financial situation.
Lastminute believes speculators are behind the fax
Lastminute believes the fax, which claims it was going to run out of cash, was the work of investors who stood to profit if its shares fell.
"It was inaccurate and there's evidence a false market in its shares was created," said spokesman Neil Bennett.
Lastminute recently reported losses which were lower than expected.
Earnings before tax and depreciation in the last three months of 2004 came in as a deficit of £1.8m ($3.3m), but some analysts had expected a £4m loss.
Announcing the results, Lastminute had said it had made a "solid" start to its fiscal year with growing numbers of bookings.
Lastminute now believes it fell victim to so-called shortsellers who anticipated its shares would fall on the back of poor results.
Shares in Lastminute.com closed higher on 10 February after the results were released, but lost about 5% of their value when the fax started to circulate in the City last week.
Lastminute's chief executive Brent Hoberman told the BBC the company had an obligation to its shareholders to report the matter to regulators.
"It is another case of market abuse where people are profiting from wrong information," he said.
The "scaremongering" fax cited some wrong figures - for example, it said Lastminute.com's pension liabilities were £30m when they were £30,000, Mr Hoberman said.
Lastminute.com had cash reserves of £30m and a £20m overdraft facility that was unused, he added.
"The fact is that we did use up cash in the first quarter of the year where we only make 20% of our sales," Mr Hoberman said.
But he added Lastminute was a "very seasonable business" and expected to generate "significant" cash flow for a third year in a row.
He said the company was in no danger of running out of cash as the writer of the fax claimed.
"It was just pretty naive analysis," Mr Hoberman said.