Official figures show that there was a sharp rise in the number of people on the Live Register in June, while the unemployment rate moved up to its highest level since 2003.
Employers' group IBEC said there were signs that the labour market was beginning to weaken for the first time in a number of years, with the downturn likely to be linked mostly to the construction sector.
The headline figure jumped by 12,353 from May to 166,363. The number of people on the Live Register usually rises in June, but the seasonally adjusted figure also rose sharply, by 3,600 to 163,400.
The unemployment rate was 4.6%, the highest level since September 2003. The last quarterly national household survey, which is regarded as a more accurate measure of unemployment, recorded 4.4% for the first three months of the year.
A breakdown showed the Live Register numbers rose in all regions, with the largest increases of 9.4% coming in the Midlands and West regions.
'The scale of the June increase confirms that the Irish labour market is experiencing some deterioration,' said economist Fergal O'Brien.
He pointed to the big increase in the number of men on the Live Register, which suggested jobs were being lost in areas such as building.