Rating agency Moody's is forecasting Lloyd's will face four years of consecutive losses between 1997 and 2000 years of account.
It adds that there is no guarantee the market will make a profit in 2001 without a significant hardening in rates.
Moody's predicts losses that for 1997, 1998, 1999 and 2000 will be £149m, £771m, £775m and £496m, respectively.
Three-quarters of the syndicates underwriting in 1998 are expected to make losses – a third of these are forecast to produce losses in excess of 15%.
"The severity of this current down cycle in worldwide insurance is illustrated by the large forecast losses for Lloyd's," said Mark Hewlett, managing director of Moody's European Insurance Division.
"The figures reflect ever-worsening loss ratios, but also the fact that we currently expect about 75% of 1998 and 1999 trading syndicates to be loss making.
"We believe that a significant hardening in rates will need to occur if the 2001 year of account is to return a profit."
Marine is now predicted to be the worse performing sector in 1999 and 2000.
But each of the main Lloyd's sectors are forecast to make losses for 1998, 1999 and 2000.
The motor sector, which is expected to make an 18% loss in 1998, looks set to produce six consecutive loss years from 1995 to 2000.
But, Lloyd's has also just released its US premium income results for 1999, showing significant growth across virtually all categories of business.
US premiums have increased 17% in 1999 to $4.8bn. Property business accounted for 38% of Lloyd's total US income, general liability for 25%, accident and health business for 11%, aviation for 10% and marine for 7%.
Income increases were particularly seen in the areas of property, general liability and accident and health.
Reinsurance accounts for more than $2bn worth of total US premiums.
Lloyd's direct business also grew in 1999. Surplus lines premiums increased the most, jumping 21% to more than $1.9bn in 1999 from $1.6bn in 1998.