The number of people on the Live Register increased over the past month when seasonal factors are taken into account.
The seasonally adjusted Live Register total rose from 158,200 in April to 159,800 in May, an increase of 1,600. This compares with an increase of 700 in April.
The Central Statistics Office said the unadjusted figure was down 309 to 154,010. The unemployment rate moved up to 4.5 per cent.
The monthly increase in the Seasonally Adjusted series consisted of an increase of 900 males and 800 females.
Irish National Organisation for the Unemployed senior policy officer Bríd O'Brien said the increase, in a week where job cuts had been announced, was a "worrying development".
"It also appears to be part of a wider trend," she said.
"Our information section have been struck recently by the number of calls they have received from people who are finding it very difficult to get a job because of their age. There is a presumption out there that given 'full employment' anyone who wishes to get a job can. Unfortunately, that has not been the experience of many people who have been made redundant."
The INOU called on the incoming Government to pursue "an active labour market policy that ensures that anyone who wants a decent job can get it; and to address the over reliance on key sectors like construction, health and education which have been the major areas of employment growth in recent years".
Labour Party TD for Cork South Central Ciarán Lynch also expressed concern.
He said the increase in the live register figure, as well as the news that Dell is planning to shed 450 jobs and the warning from AIB that demand for labour in construction and manufacturing is likely to slow down, "all point to the need for a more pro-active approach by the incoming government to job creation and job retention".
"The Dell announcement is now part of a worrying trend of the loss of relatively well paid jobs in the hi-tech sectors and shows that we can no longer rely on an endless stream of projects from multi-national computer companies to meet our job needs," he said.
He said Cork has suffered particularly in recent months with the announcement of major losses in companies such as Motorola and Pfizer.