"We have taken quite a strong position," Maechler told a Swiss Finance Institute event in Zurich, saying such a move could lead to the public holding accounts with the central bank as well as with commercial banks.

If customers became "worried or mad with a particular bank, you could transfer the money overnight to the SNB," Maechler said. "This would add a lot of risk and volatility to the system which is ultimately not needed."

(Reporting by John Revill, editing by Noele Illien)