Converium, the struggling Swiss insurer, has been forced to launch its Sfr533m (€344m) rights issue at a steep 75% discount following downgrades from ratings agencies and the failure of shareholders to approve a strategic partner investment.

Credit Suisse First Boston and JP Morgan are underwriting the issue at Sfr5 per share, a 74.4% discount to the closing price of Sfr19.55 on Monday and down from Sfr82 at which it floated three years ago.