The Bank of Spain has promised to cover up to 20 billion euros ($27 billion) in losses at Caja Mediterraneo as it seeks to offload the troubled savings bank, a newspaper said Monday.
The Bank of Spain took control of the bank in July and is now trying to sell it off.
According to the daily El Mundo, the central bank let investors know it would cover up to 20 billion euros of losses, the estimated amount of property-related assets at risk in Caja Mediterraneo (CAM), if necessary.
If confirmed, the central bank intervention would be "the costliest for the public treasury in Spanish financial sector history," the newspaper said, without identifying its source.
The price tag could unnerve financial markets -- it is equal to a government estimate of the maximum cost of recapitalising Spain's entire banking sector.
Contacted by AFP, Bank of Spain officials were unable to respond immediately to the report.
The Bank of Spain injected 2.8 billion euros and opened a three-billion-euro line of credit for the CAM when it took control of the institution in July.
But in early September CAM revealed a first-half loss of 1.136 billion euros and a high 19-percent ratio of bad loans, mostly property-related credits whose recovery was doubtful.
The average bad loan ratio for the Spanish banking sector was 6.416 percent in June.
According to El Mundo, the Bank of Spain is trying to complete the sale before general elections set for November 20.
It said rival banks Santander, BBVA and CaixaBank, as well as a union of three Basque banks, were among candidates to buy the CAM, with Santander the favourite.