Zurich Professional increased its share of the solicitors' professional indemnity (PI) market by 40% this year.
Zurich Professional wrote £28m of business in the latest round of renewals, said marketing manager Tine Thorsen.
It is understood Zurich won £20m of premium income last year.
Total premiums for solicitors' professional indemnity insurance rose 6% to £162m this year, but this rise was outstripped by the 10% rise in solicitors' fees, according to figures released by St Paul.
It claims it is the biggest company in the market, with £40m of premium income, representing 20% to 30% of the market, and says it insures most of the top 30 commercial firms.
London general manager Paul Cusition said: “We believe we are establishing ourselves as the insurer of choice for quality firms.”
QBE International said the value of solicitors' PI insurance it had written rose from £23m to £24m. QBE underwriter for solicitors' PI, Mark Casady, said the number of risks written had fallen as it took the chance to enhance the quality of its book of business.
Industry experts said Independent Insurance' demise did not affect the market, as it is understood to have written less than £1m of solicitors' PI insurance last year.