Lloyd's biggest managing agency Limit this week warned that profits for 1999 are likely to slump to £25m before tax compared to 1998's profits of £53.4m.
Limit blamed poor results in the last quarter of the year for the slide, particularly in the areas of excess of loss reinsurance and direct marine insurance.
Forecasts for 1999 on Limit's managed syndicates are for losses of between 7.9% and 2.9% on a capacity of £744m.
Its newly-acquired motor syndicate Torch is expected to suffer losses of £18.8m on an underwriting capacity of £53.7m, but is not part of the overall results.
Limit chairman Jonathan Agnew said: "This was the first year impacted by the highly competitive market conditions which have prevailed for the three most recent years of account and we expect that these results will compare favourably with the average of the Lloyd's market."