The Kantar Worldpanel survey showed almost all supermarkets, with the exception of Tesco, gained sales as measured in euro, as shoppers in the Republic spent €2.35bn on groceries in the latest quarter, up from €2.26bn a year earlier.
Price rises across the typical basket of food, drink, toiletries and confectionery in the 12 weeks to the week ending November 6 came in at 0.7%, down from a previous reading of 1.3%, it said.
Kantar won’t say whether the decline in grocery price inflation is because of the surge in the value of the euro against sterling.
The strong euro, which has climbed 12% against the pound since the June 23 vote and by over 20% since November 2015, should mean prices in supermarkets are considerably cheaper because many household goods on the shelves are shipped in from Britain.
However, the supermarket survey appears not to show any appreciably large shift in shoppers from the Republic travelling North to cash in on currency gains.
Dunnes secured a 22.6% share of all customers’ spend in the survey, up from 22% a year earlier, and winning the top slot by value of sales. Even small changes in market shares in a multi-billion market, particularly if the overall market is expanding, will have big effects on takings.
“Dunnes’ strong performance is largely down to its continued success in encouraging shopping trips via its Shop and Save promotional campaign,” said Kantar director David Berry.
“Persuading shoppers to add one extra item to every basket — worth €3.20 on average — may not sound like much, but across the country this adds up to an additional €2.8m each week”, he said, saying toiletries, alcohol, frozen food and confectionery performed particularly well for Dunnes.
The share of the market controlled by SuperValu also rose, and its market share of 22.4% secured its position as the second largest supermarket. Its share of a growing market was nonetheless down from 22.8% a year earlier, according to Kantar.
In third place, Tesco was the only supermarket whose sales fell in the quarter from a year earlier.
Its 21.4% grocery market share compares with 22.4% in the same period in 2015.
There was little separating the German discounters, with Lidl pipping Aldi for the fourth slot with a market share of 11.4% compared with its rival’s 11.3%.
“Lidl’s share of the market has increased slightly to 11.4%, with sales growth of 5.3%,” Mr Berry said.
“Aldi’s strong performance continues with sales growing by 6.6% year on year leading to a healthy increase in market share from 11.1% last year to 11.3% in the past 12 weeks.
"Aldi has seen the biggest boost to its shopper numbers during the latest quarter with an extra 40,000 households visiting the retailer and also returning more often,” he said.
Other stores, including Centra, Spar, Marks & Spencer and Boots, have a combined grocery share of 10.9%, up from 10.4% a year earlier. This group also posted the single largest increase in sales, up 9.6% by value, from a year earlier.