SVB said rates for specialty lines increased by 38% in the first half.
The group reported average premium rises of 26% across all classes of business.
It will boost its capacity by 19% next year to £521m from £438m.
The increase will be concentrated on Syndicate 1007 which writes specialty lines and will see capacity increased to £235m from £151m.
Syndicate 2147's capacity will remain unchanged at £286m.
The group expects to provide at least £473m, or 90.8% of the capacity, compared to £406m or 92.7% in 2003.
