Delegates at IMPACT's biennial conference in Kilkenny have rejected a motion calling for a "no" vote on the Croke Park public sector pay deal.
The union is recommending its 60,000 members accept the proposed deal, saying it is the best that could have been secured in the current circumstances.
Members are currently being balloted and the results will be known on June 11.
Meanwhile, the incoming general secretary of IMPACT has criticised attempts by political groups to influence internal union decisions.
In his acceptance speech - after being ratified as Peter McLoone's successor - Shay Cody stressed the independence of the union.
He also criticised the Government's current approach to reforming the public sector.