Insurer Direct Line said gross written premiums fell 5.8% in the last quarter to £854.5m compared the the same three months in 2017.
The company was hit by the ending of partnerships with Nationwide and Sainsbury's which led to a £51.3m fall in premiums.
Boss Paul Geddes, said: "The group's performance during the quarter was robust in a competitive market. We continued to grow our direct own brands in-force policies while maintaining discipline on loss ratios."
Motor premiums fell 1.2% over the year to £456.4m.