Economic analysts are forecasting a continued rise in the level of long-term unemployment.
A new CSO report shows there were 308,500 people out of work at the end of June, a rise of 4,000 or 1.3% on the same time last year.
However the number of people unemployed for more than 12 months increased by 20,600 or 12.5% during the period to almost 185,000.
It means that long term unemployment accounted for 59.9% of the total jobless number - figures not seen since the late 1990s.
Brian Ring from the CSO said that it compares to a long term unemployed level of 54% last year, and 43% in 2009:
"The long-term unemployment rate was 8.8% in the second quarter of 2012, that's up 1.1 percentage points from the long-term unemployment rate of 7.7% this time last year," he said.
"In the second quarter of 2012, three in five of all unemployed persons were long-term unemployed."
Joe Durkan, an economist at the Economic and Social Research Institute, said that the proportion of long-term unemployed will get worse before it gets better.
"You'd expect the long-term rate to continue to rise," he said.
"That only usually begins to turn around when you start to get a fall in unemployment, and even then it'll lag by a fair amount, because the first people who will get jobs will be people who are unemployed for the shortest period of time, that's what you'd normally expect.
"So I think the long-term rate will continue to rise for some time yet."