New official figures show that retail sales rose 1.3% last month on the April figure, but decreased 2.1% annually.
The CSO figures show that the trading environment for retailers remains challenging, and that motor trades provided a significant boost.
If motor trades are excluded, the volume of sales decreased by 5.1% last month compared to May 2010, and by 0.6% compared to April of this year.
The vehicle scrappage scheme ends tomorrow.
A breakdown of the figures shows that motor trades (+13.0%) and electrical goods (+2.9%) were the only categories that showed year-on-year volume increases.
Motor trade volume increased 7.4% on the April figure, which was itself a 1% decrease on the March figure.
Hardware, paints and glass (-13.9%), other retail sales (-10.3%) and fuel (-9.9%) showed year-on-year volume decreases.
Bar sales were down 8.1% annually, and down 2.6% on the April 2011 figure.
Clothing, footwear and textiles volumes were down 4.9% on the April figure and showed a 7.8% annual drop.
The value of retail sales decreased by 1.5% annually last month, though there was a month-on-month change of +1.1%.
If motor trades are excluded, there was an annual decrease of 3.5% in the value of retail sales and a monthly decrease of 1.2%.
Retail Excellence Ireland said that the figures showed that consumer confidence remained at record low levels.
'Urgent Government action is required to allow vulnerable retail operators to continue to trade,' said David Fitzsimons, REI chief executive.
Fitzsimons said that immediate intervention was needed and called for a ban on upward-only rents; a reduction in local authority rates through greater efficiency and a broadening of the tax burden to include residential users of services; the abolition of JLCs and rigorous enforcement of current retail planning guidelines.
'If Government does not act on these matters prior to the summer recess, more retail jobs will be lost,' he said.
The figures were broadly in line with expectations, according to Alan McQuaid of Bloxham stockbrokers.
These latest figures provide further evidence that a two-speed economy is still very much in place in Ireland at present, McQuaid said.
He said that the export sector continues to do very well, helped by improved competitiveness and strong global demand, but that the domestic side of the economy continues to struggle.
Dermot O'Leary of Goodbody stockbrokers highlighted the significance of core retail sales (excluding motor sales).
While headline retail sales rose by 1.3% mom (month-on-month) in May, this gain can be fully attributable to an increase in car sales, he said.
This, in turn, is partly due to a last-minute rush to take advantage of the car scrappage scheme.
A truer gauge of trends is core retail sales, which fell by 0.6% month-on-month (-5.1% year-on-year).
