The Central Statistics Office says public-sector workers were earning around one-fifth more than their equivalents in the private sector two years ago.
In an analysis of the National Employment Survey for October 2007, the statistics agency says unadjusted weekly earnings were 32.6% higher in the public sector.
However, when factors such as education, experience and working hours are taken into account, the differential falls to 19.1%.
The analysis shows that men in the public sector were earning almost 15% more than their equivalents in the private sector, while women were earning almost 23% more.
The differential was also more pronounced among those on lower levels of pay.