Switzerland's largest life insurer, whose motto is "Discover another world of financial prosperity", discovered it had miscalculated the value of its bonds, after earlier admitting it had incorrectly valued its share portfolio.

"The new reporting error is very regrettable," Chief Executive Roland Chlapowski said in a statement.

Shares fell by 11.5% to 150 Swiss francs in early trading after it said its first-half net loss was actually 578m Swiss francs (£247m; $382.8m), 192m francs more than first reported.

The revelation comes as the cash-strapped company prepares for a 1.2bn franc issue of new stock to cover the companies liabilities.

Double trouble

Swiss Life had already restated its earnings for the first-half of 2001 to show a net loss of 1m francs, rather than a profit of 253m after it misinterpreted the value of shares in its portfolio.

Company officials told reporters in a conference call that there was no connection between the errors and that controls would be tightened.

Auditors PricewaterhouseCoopers said it found the mistake while reviewing Swiss Life's results and would strengthen its internal controls.

Swiss Life has been suffering a similar fate to other insurers due to the heavy falls on stock markets and the cost of meeting fixed-returns on policies.

Its shares have fallen by more than 75% this year but they have recovered slightly from the low of 102.5 francs hit on 10 October.