Kerry Chilvers, brands director at Direct Line Group, and Dan Titley, head of marketing communications at Green Flag, are running the review. ISBA is working on the process.
CHI & Partners picked up the business in 2010.
A spokesperson for Green Flag said: "Green Flag is at an exciting juncture in its evolution, so the time is now right to explore the market to evaluate lead creative agencies. Green Flag have been delighted with CHI’s contribution to business growth over the years and we will of course be asking them to take part."
Direct Line Group called a review of its eponymous brand in December 2013 after eight years with M&C Saatchi. Saatchi & Saatchi picked up the account in March 2014 and has since relaunched the insurer.
MediaCom handles media planning and buying for Direct Line Group and successfully defended the business in reviews in 2011 and 2013.