Grand Union has declined to repitch and the review will be handled by the AAR.
Though neither party would comment on the reason for the decision, the split is thought to be down to creative differences.
HomeChoice has traditionally followed a sales-driven advertising approach, and in March handed its above-the-line account, also held by Grand Union, to Mother. Mother's first campaign is expected to launch later this year.
Grand Union worked on the account from 2003. After winning the business, Matt Nicholls, a partner at the agency, was seconded to the client's marketing department, where he worked on building brand strategy. The agency has since worked on above-the-line, direct mail and digital campaigns.
Vicky Mitchell, the director of marketing for HomeChoice, said: "Grand Union has done a great job for us. As a company, we now have the opportunity to review our situation, prior to the next stage in our marketing strategy later this year."
HomeChoice is available in 2.4m homes in London and Stevenage.
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