Britain's biggest supermarkets, including Tesco (TSCDY) , Sainsbury's (JSAIY)  and Walmart's (WMT)  U.K. unit Asda, are all suffering from sales declines amid a sharp rise in food price inflation and increasing competition from low-cost rivals.

Walmart's U.K. unit was the worst hit, with sales falling 1.8% to £4.07 million ($5.05 million) over the 12 weeks ending March 26, according to data published Tuesday by Kantar Worldpanel.

The FTSE 350 Food & Drug Retailers Index was down slightly in Tuesday morning trading. It has lost 3.73% over the past year.

 A late Easter weekend also factored into a drop in sales.

READ MORE: Walmart Feels Bite From Rising U.K. Inflation

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