The Retail Intelligence survey compared the prices of 17 products between last July and June this year. At Dunnes prices jumped 14.6%, while Tesco showed a 10.6% rise on an 18-item comparison.
At Superquinn, a comparison on 19 products found prices had gone up by 12.5%.
But the three chains, which between them control more than half the E8bn Irish grocery market, vigorously disputed the findings, arguing the survey sample was too small to be reliable. Tesco said its figures showed price rises running at 4%.
Some of the biggest increases were on fruit and veg, with tomato prices at Dunnes rising 41% in 11 months, while a medium-sized cucumber went up 90%.
Dunnes said bad weather had pushed up the cost of some imported produce and prices should fall when Irish supplies became available.
A spokesman for Retail Intelligence said the survey indicated changeover to the euro "has certainly triggered price increases, and that is what most consumers feel".
A separate survey by the Market Research Bureau of Ireland said over 80% of those interviewed believed retailers and manufacturers had used the euro's arrival to increase margins by pushing up prices.