The Labour Relations Commission handled almost 17,000 complaints last year, its highest ever number.
At the launch of its annual report in Dublin, the LRC said it handled 15,671 separate complaints from individuals last year, up from 14,500 the previous year.
It also handled a further 1,500 complaints from groups.
Chief executive of the LRC Kieran Mulvey said the spike in complaints was a symptom of the recession.
"Some people (who lost their jobs in the recession) may have out-standing pay, may not have been given appropriate notice. Some people may have been unfairly selected for redundancy," he said, and added a considerable number of complaints had come in from the areas hardest hit by the recession - hotels, catering and construction in particular.
Meanwhile, as one of the major brokers of the Croke Park Agreement, Kieran Mulvey said he expected the deal to survive through to 2014, and warned that it could not be allowed to fail.
He said if the agreement failed, "we would end up with strikes and demonstrations".