Trenwick's share price tumbled after it announced losses seven times greater in the fourth quarter of 2002 than the year before.
The US stock fell 9 cents or 18.75% on 21 February after Trenwick revealed losses of $198.1m (£125.7m) in the fourth quarter. It lost $26.4m (£16.4m) in the fourth quarter of 2001. It slid another 7.7% on Monday and on Tuesday it was at 36 cents.
The greatest factors in the loss were a $106.6m (£67.6m) charge to increase reserves and a $95.7m (£60.4m) charge to set up an allowance against fears that Trenwick may not get tax benefits from past losses in the UK.
Its gross written premium in the fourth quarter was $277.1m (£176m), down from $391.5m (£247.4m) in the period before.