Portsmouth's administrator Andrew Andronikou fears that Her Majesty's Revenue and Customs will lodge an appeal later this week against the club's Company Voluntary Agreement.
The Championship club have offered creditors 20 pence in the pound but HMRC are believed to be unhappy with the arrangement.
If an appeal is lodged, Pompey would remain in administration until the hearing and would be unable to sign any new players as they would still be under a Football League transfer embargo.
Andronikou told The News: "We're gearing ourselves up for the appeal process. We were due to get a conference call but that's been called off.
"The indication is that they aren't going to be talking to us before the end of the appeal deadline."
Meanwhile, Papa Bouba Diop has left the club and John Utaka is set to follow him out of the Fratton Park exit door.
Senegal international Diop has moved to AEK Athens while Pompey boss Steve Cotterill said of Utaka: "There's a move on the cards for John. I think something could definitely happen there.
"Unfortunately now, what we're going to be doing is loaning because a lot of the free transfers are gone. It's a tough situation but it's a top club."