The Enquirer has been contacted by a group of suppliers who claim they have been left out of the negotiations which saw Durtnell agree a company voluntary arrangement (CVA) with creditors brokered by Begbies Traynor.
Durtnell ran into financial trouble last month after trading since 1591.
Brighton and Hove City Council said the firm was no longer working on its £21m Dome Corn Exchange and Studio Theatre refurbishment job.
Creditors owed more than more £8m have agreed to give Durtnell more time to pay its debts under the CVA.
But a string of subcontractors who claim to be owed cash by Durtnell said they have not been officially listed as creditors yet and had no say in the CVA discussions.
One said: “We were still reeling from the news that the company was in financial trouble when suddenly a deal has been struck without consulting us.”
The companies have written to Begbies Traynor asking for an explanation.