German discount grocer Lidl continues to claim the strongest sales growth in the Northern Ireland market with till receipts up 6% at its 38 stores here, according to the latest data.
But information company Kantar Worldpanel said Tesco - which has around 50 local stores - remained the biggest operator here, with sales growth of 2.7% and an increased share of 35.2%.
Kantar, however, also reported that growth in the local grocery market was subdued, with sales up just 1.6% over the 52 weeks to May 20.
And despite plans for it to open its 18th store here, Asda's sales were down 0.4%.
The company, which is part of US giant Walmart, claimed a 17% share of the market.
Sainsbury's, which has 14 local stores, maintained a 17.3% share of grocery spending, and its sales were up 1.6%.
Douglas Faughnan, consumer insight director at Kantar Worldpanel, said: "Market growth in Northern Ireland remains subdued compared to the levels we saw at the end of 2017, with sales rising just 1.6%.
"Tesco continues to lead the way and outperformed the overall market with sales growth of 2.7%, increasing its share from 34.8% to 35.2%.
"Following three months of growth, Asda has seen sales decline by 0.4%. The retailer captured 17% of the market and dropped back into third place behind Sainsbury's, which has maintained its 17.3% share.
"Lidl remains the fastest growing supermarket in Northern Ireland with sales up 6.1% compared with this time last year."
Asda has announced it is planning a 40,000sq ft store at the former Nortel site at Mallusk outside Belfast. The store would create around 250 jobs.
It remains on course to merge with Sainsbury's in a £12bn deal that will allow it to further invest in lower prices, although the tie-up still requires regulatory approval.
Sainsbury's boss Mike Coupe has said the merger will produce £500m in cost savings.
Consumers have been promised cheaper everyday items, although it is not yet known where the price cuts will fall.
The Competition and Markets Authority is scrutinising the deal and it is expected scores of stores will have to be offloaded as part of the competition review.
It's been claimed that a Sainsbury's and Asda tie-up will enable them to increase their Northern Ireland customer base "considerably".