The latest figures from the Central Statistics Office show that the number of people signing on the Live Register increased again in June.
Separate figures also showed big increases in the number of redundancies notified to the Department of Enterprise, Trade & Employment.
The general secretary of the Irish Congress of Trade Unions, David Begg, described the latest unemployment figures as a 'mega-crisis' and urged the Government to invest €1 billion in a job creation and protection plan.
The unadjusted Live Register figure was up 21,721 from May to 418,592. The seasonally adjusted figure increased by 11,400 to 413,500 in June, the smallest monthly increase so far this year.
But the figures show that the number of people signing on in June was almost 90% higher than in the same month last year. There was an unadjusted increase of 197,781 people in the 12 months, according to the CSO. The standardised unemployment rate in June rose to 11.9% from 11.8% the previous month.
Meanwhile, the Department of Enterprise, Trade & Employment said 6,813 lay-offs were recorded in June, up almost 134% from the same month last year. For the first six months of this year, redundancies were up more than 160% - from 16,403 last year to 42,724.
Small business group ISME called the redundancy figures 'shocking', and called for an emergency employment action plan from the Government.
Dáil exchanges over jobless figures
Earlier, Taoiseach Brian Cowen said the Live Register figures showed the slowest rate of increase since January. But Fine Gael leader Enda Kenny said the economy was in crisis, and that the Department of Finance was in paralysis.
The Labour leader Eamon Gilmore said the Taoiseach's comments were akin to saying the country was sinking, but sinking more slowly. Mr Gilmore said there were now 200,000 more people out of work compared with last year, and this put an additional cost of €4 billion on the public purse.
Replying to a question from deputy Gilmore, the Taoiseach said he expected the unemployment rate would be in the region of 15.5% by the year's end, and could be higher in 2010.
