FirstAssist has pulled out of the Legal Expenses Insurance Group (LEIG) because the company felt "it was not the most appropriate way to lobby".
The health insurance provider ditched the group after just two months and will now consider other lobbying vehicles.
It has been associated with the Civil Justice Council (CJC) for several years.
Peter Smith, head of legal expenses at First Assist, said: "After a couple of months we decided what the group was trying to do didn't accord with what we were trying to do."
Smith added that the CJC was regarded as one of the best ways to lobby issues.
Director of the LEIG, Tony Baker, said it was still in contact with FirstAssist and expressed surprise over its exit from the group.
He said: "There was no indication they differed in any way on policies put forward by the group."