The head of the council that supervises the Swiss central bank does not expect any irregularities to be uncovered by an audit of board members initiated after the scandal that cost Philipp Hildebrand his job as chairman, a newspaper reported.

The Hildebrand case is a one-off; the culture of trust in the national bank works, Hansueli Raggenbass, the head of the Swiss National Bank's supervisory council, told the Neue Zuercher Zeitung daily in an interview published on Saturday.

Hildebrand was forced to step down on Monday after emails cast doubt on his earlier claims not to have known about a lucrative dollar trade made by his wife three weeks before he imposed a cap on the soaring Swiss franc.

Under fire over its handling of the affair, the bank council decided a week ago to get external auditors to review all personal transactions carried out by members of the governing board and their deputies between January 1, 2009 and December 31, 2011.

Raggenbass told the NZZ newspaper he was sure that the investigation would not reveal any behaviour that broke the rules because those individuals under investigation were all extremely trustworthy persons.

He added the investigation had to be concluded before the bank council could recommend a replacement for Hildebrand on a permanent basis. The council appointed his deputy, Thomas Jordan, as interim chairman on Monday.

Raggenbass said the council had already drawn up a list of possible candidates to take Hildebrand's vacant seat on the three-person, policy-setting board and wanted to expand that by the end of next week with some external candidates.

The new member of the board must be a personality with an impeccable reputation and a good international network, Raggenbass said in a separate interview with Le Temps daily.

While Jordan, an economist who has worked at the SNB since 1997, is clearly the frontrunner to take over as permanent chairman, he is seen as lacking the charisma, private sector experience and strong international network of Hildebrand.

Apart from the three current deputy board members - Thomas Moser, Thomas Wiedmer and Dewet Moser - other names mentioned as possible candidates include professor Beatrice Weder di Mauro, a member of the German government's panel of economic advisers, who would be the SNB's first female board member.

The bank council and the Swiss government are under pressure to act fast to fill Hildebrand's shoes or see the market try to test the central bank's determination to defend the cap it set on the safe-haven franc on September 6 at 1.20 per euro.

(Reporting by Emma Thomasson, editing by Jane Baird)