By Ed Ballard

LONDON--The British grocery market grew by 1.7% on the year in the 12 weeks to May 25, the slowest rate for 11 years, according to data from Kantar Worldpanel.

Of the "big four" supermarkets, only Asda Stores Ltd. increased its share of the market, with Tesco PLC (TSCO.LN), J Sainsbury PLC (SBRY.LN), and Wm. Morrison Supermarkets PLC (MRW.LN) losing ground, Kantar said.

Chains serving either end of the market performed best, continuing a recent trend. Market share gains at German discount supermarkets Aldi and Lidl accelerated, while upmarket food store Waitrose held onto its record 5.1% share.

Grocery inflation slowed for the eighth straight month to 1.2% for the three-month period, the lowest level since May 2010. Kantar said that reflects the market's price-cutting response to the success of Aldi and Lidl.

Write to Ed Ballard at ed.ballard@wsj.com

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