Deloitte says Hull need £23m "to meet current liabilities" and, if they go down, losing the £7m they get from the Premier League would be a major blow.
But the accounts cover the year before Hull's first Premier League campaign and the directors say the financial situation is much improved since then.
Hull, who are third from bottom of the Premier League, lost nearly £10m during the 12 months to July 2008, says Deloitte. During that time, the Tigers were promoted to the top tier via the play-offs.
Deloitte warns that even if they stay up this season, Hull, who avoided relegation on the final day of last season, would need to raise £16m on top of the £7m they get from the Premier League.
That money could be raised by selling players, boosting match-day revenue or through borrowing, Deloitte suggests.
Bad news but could be worse because the accounts are old accounts nickeasthulltiger Deloitte added: "The directors acknowledge that player purchases and sales are uncertain in terms of timing and quantum and some uncertainty exists over the availability and quantum of additional facilities should such be required.
"These conditions indicate the existence of a material uncertainty which may cast significant doubt about the company's ability to continue as a going concern."
However, the club's directors say they are confident they can meet the liabilities because revenue has increased by at least £40m since they were promoted to the top flight.
In a statement, they said they have "reasonable expectation the company has adequate resources to continue in operational existence for the foreseeable future".
They added that the relationship with their bankers was "strong" and that they would review the club's borrowing needs once they know whether or not relegation has been avoided.
Football finance expert Tom Cannon, a professor at Liverpool University, said: "The reality is that Premiership football clubs are living beyond their means.
"The only solution at the moment for most clubs is some kind of fairy godfather from the Middle East or Asia."