"Of course I am disappointed. FINMA has given us directions as to how we should strengthen capital. We are fulfilling those," Dougan told the SonntagsZeitung paper in an interview.

"Even more surprising were the suggestions by the SNB to cut the dividend and to raise capital."

In its annual financial stability report published on Thursday, the SNB said Credit Suisse should urgently boost its loss-absorbing capital base by cutting risk, suspending dividends or issuing shares, sending the stock down 10 percent.

While it is the SNB's job is to guard the stability of the Swiss financial system, the FINMA regulator polices the banks and has not demanded any immediate action from Credit Suisse.

Dougan rejected the idea of a capital hike: "That is not our plan".

He said the SNB's calculations of Credit Suisse's capital were incomplete and based on a very pessimistic scenario for the euro zone debt crisis, adding the report had shaken the confidence of clients and investors: "That is not just bad for us but for the whole financial center."

Dougan said SNB Chairman Thomas Jordan had not discussed the need for Credit Suisse to cut its dividend and raise capital when the two men met for lunch just 10 days ago.

The SNB calculated that Credit Suisse had a Tier 1 capital ratio of 5.9 percent at the end of March, compared with 7.5 percent for rival UBS (UBSN.VX), as calculated under global Basel III rules which demand banks reach 10.5 percent by 2019.

The criticism from the SNB has also increased pressure on Dougan, who was lauded for navigating the bank through the subprime crisis relatively unscathed but has come under fire of late for squandering that advantage.

Credit Suisse responded on Thursday by noting it exceeded current Swiss capital requirements and was working towards meeting stricter rules by 2019, already issuing loss-absorbing contingent convertible bonds and pursing a plan of building up common equity by retaining earnings and cutting assets.

Oswald Gruebel, a former Credit Suisse CEO, said the bank's shares had fallen so much on Thursday because shareholders were afraid that the bank would have to raise capital.

"But CS also has the possibility to cut its balance sheet and thereby indirectly increase its capital, or do both," Gruebel wrote in his weekly column for Der Sonntag newspaper.

But Hans Geiger, a retired Zurich University banking professor and a former senior executive at Credit Suisse, said the bank was ill advised to try to fight the SNB.

"The reaction of CS is fatal," Geiger told the Tages-Anzeiger newspaper on Saturday. "Whoever goes on a confrontation course with the national bank has lost their reason."

(Reporting Emma Thomasson; Editing by Alison Birrane)

• A Permanent Economic Emergency