The number of people on the Live Register rose to 170,701 in January, an increase of 4,559 on the December figure, according to figures from the Central Statistics Office.
The seasonally adjusted figure rose by 2,300 to 167,000, the sharpest rise since June last year and the highest figure for three years. The number of people claiming has now risen by 10,741 over the past 12 months.
There were monthly increases in all regions of the country, with the largest rises coming in counties Meath and Kildare.
The unemployment rate is now 4.5%, up from 4.4% in December.
The Irish National Organisation of the Unemployed said the rise in youth unemployment was particularly worrying - up 11% since December 2001.
Friends First chief economist Jim Power said, 'Given the serious difficulties that have plagued the global economy over the past couple of years and that continue to intensify, and the sharp slowdown in Irish economic growth over the past year, the Irish labour market remains amazingly resilient.'
But Power warned that it was inevitable that the coming year will see an ongoing deterioration in the Irish labour market.
