The seasonally adjusted Live Register rose by 2,600 in May, bringing the total number of people signing on to more than 443,000.
The increase pushed the standardised unemployment rate slightly higher in May to 14.8 per cent, compared with 14.7 per cent a month earlier. The rate is currently 1.6 per cent higher than that recorded in May 2010.
The Live Register also includes casual and part-time workers.The official unemployment rate is measured by the Quarterly National Household Survey, which showed the rate was 14.7 per cent in the fourth quarter of last year.
There was a monthly rise of 2,200 in the number of men signing on, with an additional 400 women joining the register in May. However, in the year to May, the number of men signing on fell by 0.7 per cent, or 2,095, to 288,290, while the number of women rose by 3.5 per cent, or 5,120, to 152,657.
The number of casual and part-time workers rose by 7.7 per cent over the year, with 84,933 signing on. Workers of this type now account for 19.3 per cent of the register.
Unadjusted figures on the register showed a total of 440,947 people signed on in May, a rise of 3,025 or 0.7 per cent over the year. However, the Central Statistics Office said the rise was less than that recorded in April 2011, when it rose by 1.6 per cent.
Analysts had been expecting a decline in the Live Register, although they did note that any decline in unemployment rates would be more likely to reflect increased emigration and a greater number of people staying on in education than a fundamental improvement in employment prospects.
Bloxham Stockbrokers earlier today it believed any improvement in job conditions would not be seen until the latter part of the year at the earliest.
The number of long-term unemployed was causing concern among analysts.
"In addition to the high levels of benefit claimants, a further problematic feature of the Irish jobs market is the make-up of the pool of unemployed workers. An increasingly large proportion of total claimants is being accounted for by those who are long-term unemployed, ie those who have been continuously registered for benefits for over a year," Ulster Bank economists Lynsey Clemenger and Simon Barry said in a note.
"The total falling into this category has risen sharply over the downturn, as workers who have lost their jobs have found it extremely difficult to regain employment."
The number of people who have been signing on for more than a year rose to more than 176,300 in May, a 6,900 increase on the figure recorded in April.
"The number of such individuals has now doubled since October 2009, as the share of long-term claimants in the total has gone from 21.2 per cent at that time to 40 per cent in May of this year," Ulster Bank said.
"While labour market activation measures targeting the long-term unemployed were a feature of the Government's recent Jobs Initiative, today's numbers highlight the extent of the problem in this area."
The Irish Congress of Trade Unions said the increase in the register was an indication that austerity measures had failed and was "clear proof" of the need for a policy change at both the European and domestic level.
Ictu's economic advisor Paul Sweeney said the rise was a "direct consequence of official policy".
"Deflation is simply not working and is leading directly to job losses. We have seen domestic demand crash by over 25 per cent in less than three years. That translates into thousands of job losses and thousands of families in very difficult circumstances," he said.
"This is not the route to recovery, but leads precisely in the opposite direction. It is time that the authorities at the EU level and here at home stopped taking counsel from the advocates of austerity. It doesn't work. Today's figures are proof positive."
