German discount retailer Lidl has increased sales in its Northern Ireland supermarkets by nearly 6% over the last year, latest figures show.
Research organisation Kantar Worldpanel said the company, which has 38 stores here, had also increased its share of the grocery market to 5.7% in the 52 months to August 12.
And the organisation said Lidl's relatively modest market share left it with plenty of room for growth.
Tesco, which has around 50 stores of various sizes around the province, had boosted its sales by 2% and grown its market share slightly to 35.3%, enabling it to strengthen its position as our number one supermarket.
Overall, spending in the local grocery sector had grown 1.4% compared to a year earlier.
Kantar Worldpanel said the growth in its sales meant customers of Tesco here were now spending an extra £47 over the year.
Sainsbury's market share was steady at 17.4%, while Asda was the third-biggest supermarket, with market share of 17.1%.
However, Asda had the weakest sales growth at just 0.7%, while Sainsbury's sales were up 2.3%.
Sainsbury's has 14 stores in Northern Ireland while Asda has 17, and is planning its 18th on the site of the former Nortel factory in Mallusk.
Lidl's sales growth of 5.9% was the strongest of all the major operators here.
And the category of 'other multiples' - including grocers such as Dunnes and Marks & Spencer - reported 0.7% growth in sales and a market share of 8.6%.
Sales in the category of 'total symbols' - encompassing independent retailers operating under brands like Spar and Centra - reported a fall in sales of 4.5%, while their market share was down from 8.5% to 7%.
Douglas Faughnan, consumer insight director at Kantar Worldpanel, said: "The Northern Irish grocery market is beginning to pick up, with sales growth now at 1.4%.
"Tesco continues to perform strongly: sales are up 2.2% and the retailer has increased its market share by 0.3 percentage points to 35.3%. Despite fewer customers shopping at Tesco compared with this time last year, they are spending an additional £47 each annually - a significant increase for the supermarket."
Spending at Sainsbury's stores had grown by a similar rate, he said. "Achieving sales growth of 2.3%, Sainsbury's remains the second-largest retailer and accounts for 17.4% of overall market sales.
"With average price paid per item increasing by 4.6% at the supermarket, shoppers spent an extra £41 per annum on groceries.
"Meanwhile, in third position, Asda experienced growth of 0.7%, dropping market share by 0.1 percentage points to 17.1%.
"Buoyed by sales growth of 5.9%, Lidl was the fastest growing of the major retailers and reached a record market share of 5.7%. There is still plenty of room for the supermarket to increase that share further.
"On average, shoppers buy fewer items at Lidl in comparison to the other major retailers, but it's currently the only one to see growth in basket size, which suggests that customers are finding more of the items they want at Lidl on their weekly shop."
In the Republic, Musgrave brand SuperValu is the dominant grocer, with a 22% market share.