Plans to develop Battersea Power Station in south London are in doubt after creditors applied for administrators to be appointed.
Battersea Power Station Shareholder Vehicle, the holding company behind the plans, has yet to find a partner to develop the derelict landmark site.
Lloyds Banking Group and National Asset Management Agency (Nama) have asked for the firm to be put in administration.
A court hearing has been scheduled for 12 December.
This week Chancellor George Osborne confirmed the government's backing for plans to extend the Northern Line into the heart of the planned development.
The building was acquired by Real Estate Opportunities (REO), the majority owner of the holding company, in 2006.
Some £502m of debts owing on the project have now been called in by creditors.
A statement from REO said: "The BPS [Battersea Power Station] Subsidiaries are currently not in a position to satisfy these demands for repayment.
"The company has also been advised that Nama and Lloyds Banking Group have applied to the English court for the appointment of administrators."
Lloyds said administration was always a last resort.
A spokesman said: "If another bid comes in during this time then the process can be stopped.
"We want to move it forward and secure a sale with a management team and equity that will take the development forward."
Nama refused to comment.