Public sector workers could demand a pay increase of 6% if the Government does not reduce their working hours.
The country's largest public sector union is calling for a mid-term review of their current pay deal and says restoring pre-crisis working hours is essential.
Fórsa claims civil servants now work 75,000 more hours each week than before the Haddington Road Agreement in 2013.
The Government estimates reducing working hours would cost more than €600m a year.
Speaking at Fórsa's conference in Kilkenny this evening, incoming General Secretary Kevin Callinan said if the hours are not reduced, unions could lodge a pay claim.
Mr Callinan said: "If the hours aren't reversed, it's inevitable, it seems to me, that there will be a productivity climb. The hours are worth 6% in rough figures, it varies from group to group.
"For most of our people we are talking in terms of in or around 6%, so that would be on top, that would be like an additional claim that would emerge if we don't find a way to deal with the issue."