By Ian Walker

LONDON--Sales at Wm. Morrisons Supermarkets PLC (MRW.LN) have risen for the second consecutive period supported by an increase in online shopping and it is again the only one of the top four grocers to record a rise in sales, according to a survey Tuesday.

For the 12 weeks to June 21, Wm. Morrison's sales rose 0.6% on the year to 2.79 billion pounds ($4.4 billion) and its market share rose to 11% from 10.9% in the comparative period last year.

Outside the top four, the only other grocers to increase market share and sales were up-market retailer Waitrose and German discounters Aldi and Lidl, according to Kantar, which monitors the household grocery purchasing habits of 25,000 demographically representative households in the U.K.

Waitrose sales rose 1.2% to GBP1.29 billion and its market share rose to 5.1% from 5.0% in the 12 weeks ended June 22, 2014. The combined market share of Aldi and Lidl rose to 9.4% from 8.3%. Sales at Aldi rose 15% to GBP1.39 billion, while Lidl's sales were up 9.1% to GBP987 million.

Market leader Tesco PLC's (TSCO.LN) share fell to 28.6% from 28.9%, while Asda's share fell to 16.5% from 17.1%. Tesco sales were down 1.3% over the period to GBP7.25 billion, while Asda's sales were 3.5% lower at GBP4.19 billion

J. Sainsbury PLC's (SBRY.LN) market share fell to 16.5% from 16.7% with its sales falling 1.3% to GBP4.18 billion.

Write to Ian Walker at ian.walker@wsj.com

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