Preliminary estimates from the Central Statistics Office show that average weekly earnings fell 0.8% over the three months to the end of September compared to the same time last year.
The weekly average figure fell to €671.70 compared to €677.13 the same time last year.
Today's CSO figures also reveal that average hourly earnings fell to €21.07 in the third quarter from €21.36 in the third quarter of last year, a fall of 1.4%.
Today's figures show that an improving economy is not translating into higher incomes.
The Government is forecasting growth of 4.7% this year, which would make it the fastest growing economy in the euro zone. The unemployment rate fell from 11.4% to 11.1% between June and September.
"Even with our growth levels, the level of the downturn has resulted in a lot of spare capacity in the economy, keeping wages down," said Alan McQuaid, chief economist at Merrion Stockbrokers.
"You would expect, as the recovery improves, that wages will start to pick up, but not enough to have a big impact on inflation," he said.
Average weekly earnings rose in six of the 13 sectors surveyed by the CSO in the three months under review. The largest percentage gain was seen in the industry sector, with wages there up by 3.4% from €805.44 to €832.59.
The largest percentage fall was recorded in the professional, scientific and technical activities sector with wages there decreasing by 5.3% to €750.35 from €792.27.
The CSO figures also show that the estimated number of people working in the public sector fell by 1.6% in the third quarter from 376,300 to 370,300.
The biggest fall was seen in the health sector, which registered a fall of 3.7% in the third quarter compared to the same time last year.
The biggest increase was seen in the semi-state sector, with employment numbers rising by 2.2% from 49,300 to 50,400.
