Royal & SunAlliance (R&SA) is targeting large corporate clients with the launch of a new product and the establishment of regional underwriting teams.
Jon Woodman, R&SA's director of risk solutions, said: "There is £200m worth of business out there. Within 18 months we would expect to become one of the market leaders."
Regional teams will be established in Manchester, Leeds, Birmingham and Glasgow where R&SA will underwrite property, liability and motor risks for businesses.
It is focusing on companies with annual turnover of more than £100m.
The insurer also expects to expand the teams in each regional hub to service high value clients.
For firms without insurance buyers, said Woodman, R&SA will offer a risk management and active claims management services.
He added: "[The new product] contour is the shape of things to come. We developed it with clients and brokers to offer a simple solution that can genuinely help large companies achieve their business goals."