New figures from the Central Statistics Office show that the volume of retail sales fell by 2.5% in May compared to April - the sharpest contraction in nine months.
But on an annual basis, retail sales rose by 7.4% in May compared to May of last year.
The CSO said that when car sales are excluded, retail sales fell by 2% on a monthly basis, while they rose by 5.5% on an annual basis.
Today's figures show that sales of books, newspapers and stationery rose by 7.6% on a monthly basis, while electrical goods increased by 3.2% and bar sales were up 1.2%.
The sectors with the largest monthly decreases were food, beverages and tobacco with sales down 4.8%.
Retail sales in department stores fell by 3.9% and hardware, paints and glass sales were down 3.5%.
Commenting on today's figures, Investec economist Philip O'Sullivan said that the sharp month on month decline is a little surprising given that the unadjusted consumer confidence index was effectively flat last month.
Mr O'Sullivan said it is possible that the receipt of the first set of bills from Irish Water may have served to dampen household spending.
He also said that previously released inflation data which showed that retail fuel prices jumped by 3% on a monthly basis in May, presumably led to a "re-profiling of consumer spending".
Meanwhile, Merrion economist Alan McQuaid said that "core" retail sales have now posted a positive annual increase for nineteen months in a row.
The economist said that although retail sales remain erratic on a monthly basis, the underlying trend is positive.
"Indeed, new cars sales are projected to break the 100,000 level this year for the first time since 2008, but personal spending in other areas is starting to pick up too and is becoming more broad-based. This can only be good news for retailers and employment prospects in the sector," he added.
