ZURICH – Credit Suisse Group shares plunged and the cost of insuring its bonds against default were near a distressed level after the bank’s biggest shareholder ruled out any additional support. Credit Suisse shares dropped as much as 30 per cent, triggering a 6 per cent plus fall in the European banking index, while five-year credit default swops (CDS) for the flagship Swiss bank hit a new record high, highlighting increasing investor concerns. Investors are increasingly worried about the health of banks following the collapse of Silicon Valley Bank