"Credit Suisse would not have survived Monday," Karin Keller-Sutter said, explaining the need to find a swift solution for Credit Suisse's woes.

"Without a solution, payment transactions with CS in Switzerland would have been significantly disrupted, possibly even collapsed, and wages and bills could no longer have been paid," she said.

Last Sunday it was announced that UBS had agreed to buy its rival Credit Suisse for 3 billion Swiss francs ($3.23 billion) in stock and agreed to assume up to 5 billion francs ($5.4 billion) in losses in a merger engineered by Swiss authorities to prevent more market turmoil in global banking.

Emergency law was used to enable the banks to reach a speedy agreement. Shareholders, for example, who would normally get a say in such a takeover were largely bypassed, which has angered some of them.

Keller-Sutter said the Swiss government's executive Federal Council "only went as far as was absolutely necessary to achieve the goal of stabilisation".

"If we had done nothing, CS shares would have been worthless on Monday and the shareholders would have gone home empty-handed," she said.

($1 = 0.9199 Swiss francs)

(Reporting by Noele Illien; Editing by Giles Elgood)