Credit Suisse on Thursday slammed as "incomprehensible" a shareholder's efforts to marshal opposition against the bank's plan to issue CoCo bonds, a new type of safety capital backed by the Swiss National Bank.

Earlier Thursday, activist shareholder Ethos Fund - influential in Switzerland because it holds sway with Swiss pension funds - said shareholders should vote against Credit Suisse's plan to create as many as 400m additional shares, part of which the bank needs to fulfil a Sfr6bn ($6.74bn) contingent convertible, or CoCo, bond issue sold to the government of Qatar and Saudi Arabia's wealthy Olayan family in February.