The INTO is recommending rejection of yesterday's public sector pay deal to its 36,000 members.
The decision was made at a meeting of the union's executive today.
A ballot of primary teachers will begin next week.
The union said its decision not to recommend the deal was based on "the failure of the proposed agreement to progress the issue of pay equality".
Speaking after the decision today the general secretary of the INTO Sheila Nunan said the union had made every effort to resolve the issue.
She said: "The recent pay talks were an opportunity to draw a line under pay discrimination and right a wrong imposed on new entrants since 2011. The agreement has failed to signal an to end pay inequality imposed by government on recent entrants."
The Teachers Union of Ireland is also recommending rejection of the deal, which has been dubbed ''Lansdowne Road 2'.
The INTO also said primary principal teachers had been waiting more than 10 years for the payment of an independently awarded pay uplift to help end some of the large pay disparity between primary and post primary principals.