The head of Poland's central bank is warning that a bill offering relief to holders of Swiss franc mortgages combined with new taxes on banks amount to a "recipe for a banking crisis."

Marek Belka's comments Tuesday in an interview to the private broadcaster TVN come amid heightened political uncertainty under a new populist government in Warsaw. The anxiety prompted the rating agency Standard & Poor's to downgrade Poland's foreign credit rating last week.

Belka said that a bill that promises relief to about half a million Poles with mortgages in Swiss francs could weaken the banking system. The proposed legislations would allow the mortgage holders to convert their debt into Polish zlotys at a loss to the banks.