Employment in construction firms fell by 2.3% in July compared to the same month last year.
The monthly employment index fell from 113.5 in July last year to 110.9 in July 2007.
The monthly Central Statistics Office (CSO) survey questions 1,000 private construction firms which employ five or more people.
The CSO said that the final figure for June 2007 showed a fall of 1.2% compared with June last year.
This is the weakest reading since December 2002 and confirms the moderation in the construction sector, particularly housebuilding.
Economists suspect the fall in construction employment may be bigger than that measured by the CSO as only firms with five or more employees are measured, and that their survey undersestimates the level of job losses in the sector.
Separate CSO figures showed that the average weekly earnings for clerical and operative workers in the construction industry increased from €761.83 to €795.97 in the 12 months between June 2006 and June 2007, a rise of 4.5%.
