FILE PHOTO: A sign is displayed at a Sainsbury's store in London, Britain April 30, 2016. Photograph taken April 30, 2016. REUTERS/Neil Hall/File Photo

LONDON (Reuters) - Sales at Sainsbury's SBRY.L, Britain's second biggest supermarket group, dipped in the last 12 weeks, while its main rivals all saw increases, industry data showed on Tuesday.

Sainsbury’s sales were down 0.2 percent in the 12 weeks to June 17 and its market share fell 0.4 percentage points to 15.6 percent, researcher Kantar Worldpanel said.

Shares in the group, which in April agreed to buy No. 3 player Asda for 7.3 billion pounds ($9.7 billion), were down 1.8 percent at 0814 GMT.

Sainsbury’s is due to publish a first quarter trading update on July 4.

In contrast, sales at Asda, the British arm of Walmart WMT.N, rose 1.8 percent. They were up 1.4 percent at market leader Tesco TSCO.L and up 1.9 percent at No. 4 Morrisons MRW.L.

However, all three continued to lose market share to discounters Aldi [ALDIEI.UL] and Lidl.

Aldi’s sales rose 8.2 percent and Lidl’s were up 10.0 percent, giving market shares of 7.4 percent and 5.4 percent respectively.

Overall, UK grocery sales rose 2.1 percent in the period, reflecting strong sales of spirits, soft drinks and hay fever remedies.

Kantar Worldpanel said grocery inflation was 1.9 percent, with prices rising fastest in markets such as butter, colas and canned fish.