Hiscox is expecting to increase its directors' and officers' (D&O) business by 400% in 2003.
A Hiscox spokesman said: "The D&O market is currently very constricted and we will write around five times as much D&O cover this year."
But, despite the increase, Hiscox said it would not recruit more underwriters.
Hiscox has revealed that gross written premium rose to £726m in 2002.
Professional indemnity accounts for about 8% of its £269m capacity for 2003.