Clarion is briefed to "educate" the media and consumers on the benefits of Nectar, through which shoppers collect points that count towards special offers.
The appointment follows Nectar operator Loyalty Management UK's decision to pitch the account, held by Manning Selvage & Lee since the scheme was launched by Sainsbury's, BP, Debenhams and Barclaycard three years ago.
Two other undisclosed agencies made a final shortlist in a review co-ordinated by AAR. MS&L did not take part.
Former MS&L associate director Val Burgess, who worked on Nectar at the agency, is understood to be working for LMUK on a freelance basis, having now left MS&L.
Last year, Sainsbury's said it would cut back Nectar promotion and Barclaycard stopped offering the scheme to new cardholders.
LMUK has hit back with the launch of Nectar for Business. College Hill is handling B2B PR around the trade purchase scheme.
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