Royal & SunAlliance reported disappointing 2001 results, showing a general business result of a loss of £11m which is down from a profit of £290m in 2000.
The group posted a 2001 operating result, which includes long-term investment returns, of £16m, down from £462m in 2000.
The UK's second biggest general insurance company was hit hard by World Trade Centre losses, estimated at £215m, and an increase of £384m in reserves against asbestos claims.
The company said the combined impact of these two costs "masked the solid performance of large parts of our general insurance business around the world".
The combined operating ratio for 2001 including the WTC loss was 112%.
The combined ratio shows the sum of claims and expenses divided by premiums earned. A figure more than 100% shows an underwriting loss.
Even excluding the cost of the 11 September tragedy, the underlying ratio was 104.7%, which falls short of the company's target of 102%.
Group chief executive Bob Mendelsohn picked out the UK global risk management business as being among divisions that fell short of expectations.
But he said: "UK commercial motor produced an outstanding result and continues to demonstrate how a book of business can be improved.
"Three years ago it represented one of our problem areas but it has achieved a £66m improvement in 2001 alone. UK household and health also performed strongly with combined ratios of 101.3% and 95.6% respectively."
