Sainsbury and Auchan have linked up to attract regular booze cruisers to their Calais stores, taking on Tesco and Carrefour stores based in a nearby retail park.
A joint Sainsbury wine store and Auchan bonus card, valid for one year, offers customers a free case of champagne if they get their card stamped at three visits to each hypermarket.
Customers have to spend 199 euros at Sainsbury or 1150 in Auchan each time to qualify for a stamp.
A Sainsbury spokeswoman said: "The card was set up to go to these stores, in the same retail park, rather than Tesco and Carrefour nearby. Most of our customers tell us they come three times a year. We want to work together and encourage repeat visits."
Sainsbury also signed up the Auchan store to sell its Taste the Difference Christmas puddings over November and December.
A spokeswoman said: "Auchan told us you can't buy Christmas puddings in France, and we wanted to make sure customers in Calais could get hold of one."

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