Ensign is seeking to exclude claims management companies by adding legal expenses cover to its motor policies.
The move to take action against after-the-event (ATE) premiums follows a growing trend in the motor insurance industry to stave off increasing claims costs.
An Ensign spokesman said: "Ensign is following a trend that is not evident in the Lloyd's Market.
"To make legal expenses cover mandatory minimises the need for ATE solutions in motor accident claims and makes claims management companies unnecessary."
Underwritten by DAS, the cover will be offered to injured drivers and passengers on all its commercial bus, coach and private motor policies.
DAS corporate manager Lyndon Willshire said: "If the industry accepts ATE premiums and uplifts as the norm, premiums will rocket.
"It is far better for all motor insurers to provide a low cost legal expenses insurance add-on."