Anglo Irish Bank faces losing at least £40m due to the failure of a company which owned the lease on part of the Odyssey complex in Belfast.
Odyssey Pavilion LLP, which had a 150-year lease for the part of the building containing bars and restaurants, went into administration earlier this year.
It has emerged that it puts the value of the lease at £31m while Anglo Irish is still owed £71m.
The administrator has not yet given a view on the lease's value.
The company is run by businessmen Peter Curistan and Peter Holmes.
The failure of the company is likely to also mean a significant cost to the taxpayer.
HM Revenue and Customs has made a claim for a VAT repayment of £425,869 but a report by the administrator says that Anglo must get back its money in full before anything is paid to the taxpayer.
Mr Curistan is taking legal action against Anglo maintaining that he had an offer for £74m for the lease on the table but that the bank blocked the deal because it wanted him to sell to its preferred developer.
He has served a writ and is currently compiling his case.
Anglo Irish was nationalised by the Irish government after it was badly hit by the banking crisis and billions of euros of its property loans went bad.