Sainsbury's was the worst performer of Britain's big four supermarket groups in the latest 12-week period, continuing a long run of underperformance, industry data showed on Tuesday.
Market researcher Kantar Worldpanel said sales at Sainsbury's - Britain's No. 2 grocer that is trying to buy No. 3 Asda for £7.3 billion ($9.6 billion)- fell 1% in the 12 weeks to 24 February.
Sainsbury's and Asda suffered a major blow last month when Britain's competition regulator said its provisional view was that their deal should be blocked in the absence of the sale of a large number of stores, or even one of the brands.
Kantar Worldpanel said all of Britain's big four supermarket chains lost market share in the 12-week period to German-owned discounters Aldi and Lidl.
Aldi's sales were up 10%, while Lidl's rose 5.4%, taking their combined market share to 12.8%.
Kantar Worldpanel also noted that one in 10 shoppers claim to have started stockpiling food to prepare for a no deal Brexit, echoing data also published on Tuesday from Barclaycard.