Royal Bank of Scotland's plans to offload a network of 318 branches are set to be tested after it has emerged that buyers would have to provide around £2 billion to support the business.
RBS, which is 84% taxpayer owned, is selling the former Williams & Glyn's outlets in England and Wales as part of its efforts to assuage European competition fears in the wake of its Government bailouts.
It is understood that documents sent to prospective bidders show the new owners would have to stump up capital to support the loan book.