Insurer The St Paul claims to have won more than £50m of gross written premiums in the scramble for the new solicitors' professional indemnity market.
The insurer estimates that it has between 20% and 30% of the premium pot and is the market leader for the first £1m of solicitor PI cover in England and Wales.
The disparity between the two figures reflects the general uncertainty over whether the original £250m of premiums available has now shrunk by as much as £100m due to heavy discounting.
The PI market was created when the Law Society members voted to scrap the Solicitors' Indemnity Fund, the mutual fund that previously had a monopoly of the first £1m of PI cover, in favour of the open market.
There has been fierce competition to win market share over the summer months and solicitors have reported huge price variations, some as low as a fifth of the previous SIF premium.
Analysts predict some insurers will face heavy losses over the next few years. New insurer The Underwriter pulled out of the market before the summer.
St Paul sales director David Bevan said: “Prices offered by some competitors would seem to be unsustainable, but we developed a sophisticated approach which means our quotes closely reflected the degree of risk.”
St Paul was favourite to win the lion's share of the premiums after winning the right to handle the Law Society's in-house scheme and the claims information of the SIF.
But St Paul has faced stiff competition mainly from Zurich, and the broker Aon.
The complete solicitors PI market share will emerge when the Law Society publishes the details of the assigned risk pool, the shared pool of risks for solicitor firms deemed too risky for cover.