Dunnes Stores boosted its share of Ireland's multi-billion-euro grocery market by the most in four years as heavy promotional activity over Christmas helped it steal a march on its rivals.
New data from research group Kantar Worldpanel shows that Dunnes Stores' share of the grocery market rose 4.6pc to 24.3pc in the 12 weeks to January 20.
Tesco and the Musgrave-controlled SuperValu and Super-quinn all lost ground in the period.
The decline posted by Tesco is the first time that the retailer has fallen behind the market growth rate since October 2009. In the latest period, the market growth rate was 0.6pc. Kantar said Tesco could grow its share again by capitalising on shoppers who've been making more frequent trips to its stores.
The performance by Dunnes firmly reverses what had been previously difficult trading for the family-owned retailer.
But retail insiders say the group effectively "bought Christmas" by rewarding customers with generous vouchers in the run-up to the season.
The strategy worked. Dunnes Stores was the only one of the larger multiples to pick up market share.
Tesco's market share fell 1pc to 27.6pc, but it's still the country's biggest grocery retailer. SuperValu's share slipped 0.5pc to 19.8pc while Superquinn's fell 4.5pc to 5.3pc. Aldi's market share was 5.9pc. Lidl's was virtually unchanged at 5.7pc.
David Berry, commercial director at Kantar Worldpanel, said that shoppers responded well to Dunnes' promotional 'Shop and Save' offer, buying more items when they did shop and increasing the average size of their baskets by almost €3 to €36.70, a rise of 9pc.
"This has opened a considerable gap between Dunnes and its competition, with the average Tesco and SuperValu shop standing at €30.40 and €22.40 respectively," he said.
Mr Berry said that Dunnes had performed well across a range of categories during the reported period, including fresh produce, alcohol, soft drinks, crisps and chilled convenience food.
Kantar said that grocery inflation stood at 5.2pc at January 20, up on the 5pc rate in the previous reported period. It's now at the highest level since the 5.6pc rate recorded in May 2011.