Amlin, the biggest independent Lloyd's operator, has increased its estimate of losses from 11 September.
Its estimate of WTC losses due to Syndicate 2001 on the 2001 year of account has increased to $129.7m (£85.4m), or 14.8% of capacity at quarter end rates.
In December last year the company set its estimate at £60m ($91m at today's rates) before tax, which it then confirmed on 23 January.
By 24 May the estimate had crept up to $112m (£73.8m), or 13.3% of capacity.
The company argued that the increase, of 1.5% of capacity, was offset by an increase in forecast results for Syndicate 2001, which had capacity of 69.6% last year.
The syndicate's forecast result has improved by 2.5% since 24 May.
It is now forecast to lose between 1% and 6% of its capacity, including the WTC losses.
Excluding WTC losses, the forecast changes to a profit of between 8.8% and 13.8% of its capacity.
Syndicate 2001's gross written premium income was up by 54% in the first half of 2002 compared to the same period last year.
It received £510m in the first half, net of brokerage, compared to £330m last time.
The syndicate's gross incurred loss ratio was down to 6.4% from 13% at the same stage last year.
Amlin chief executive Charles Philipps said: "The first six months' trading has been very encouraging and we are increasingly confident that this hard market will continue into 2003 and possibly beyond."
