Lloyd's has lost around £3.5bn over a four year period, according to Moody's Investors Services.
The ratings agency said accounts for 1998 to 2001 showed estimated losses of £1.1bn, £1.5bn, £715m and £165m.
Mark Hewlett, managing director of Moody's European insurance division, said: “Our continued pessimism over Lloyd's prospects for the current open years of account reflects the severity of the latest downcycle.”
Moody's is continuing to forecast a sizeable loss for 2000, despite an absence of significant catastrophe activity so far and a general improvement in rating levels.
Hewlett added: “Moody's is pessimistic about the 2001 account's ability to be profitable in a ‘normal' loss environment. That said, there is likely to be a wide variance between the results of the best and worst performing syndicates.”
But he said next year's account should be more profitable as market conditions continued to improve.
Lloyd's was unable to comment.