SNB Chairman Philipp Hildebrand resigned with immediate effect on Monday after a scandal over a currency trade made by his wife and his deputy Thomas Jordan was appointed as intermin chairman.

"Maybe April or May," Eveline Widmer-Schlumpf said at the government's weekly news conference.

"I think it's right that you have all three and then you can make the choice as a whole," she also said.

The SNB's bank council will make a recommendation to the government, which then makes the appointment.