Leyton Orient Fans Trust believe the adjournment of a winding-up order has left the club and supporters in a "state of limbo".
A High Court judge on Monday said he would consider the winding-up application of the League Two strugglers on June 12.
HMRC officials said a debt owed had been paid but the case has now been adjourned to allow Orient to pay other recurring debts - including more than B£18,000 to Central Circle Events Management Ltd, which provides matchday stewards, B£35,000 to Waltham Forest Council and B£6,000 to the club's official photographer.
Orient will not go into administration for the time being and will also avoid a 12-point EFL penalty.
Although a lawyer told the court that B£1million was due to be injected into the club soon, LOFT expressed their concern in a statement on their website.
It read: "Today's events leave the club, its suppliers, its employees and all O's supporters in a state of limbo.
"While the immediate threat of liquidation has been staved off until June, there is clearly a significant level of debt remaining. A further winding-up petition from HMRC cannot be ruled out, if the next bill for unpaid tax is treated the same way by Mr Becchetti (club owner Francesco) as the last one.
"It is clear now that the only way Leyton Orient can hope to recover as a football club, both on and off the field, is for Mr Becchetti to sell, and sell as soon as possible.
"We are also extremely grateful for the other fundraising being organised with the fund in mind - including the various memorabilia auctions, benefit gigs and other pledges.
"Our thanks to the very many supporters, of Orient and the wider football family, who have sent us messages of support in the past weeks. The fight to save Orient continues."
LOFT board member Adam Michaelson told BBC Radio London: "There are a number of still outstanding creditors, including a number more that were not represented today.
"It leaves the club in a state of significant uncertainty and, frankly, mortal danger.
"In respect of a potential sale, we would call upon Mr Becchetti now to look to sell the club at the earliest possible opportunity and make good on his promise that he's made."