The Education Minister, Joe McHugh, has expressed his disappointment after primary school teachers rejected a pay offer for 'new entrants'.
Up to 53% of INTO members voted against the proposals and the union's executive will meet next week to discuss a ballot for industrial action.
The union said the Government's offer did not achieve pay equality for newer members of the profession.
Minister McHugh said, despite the setback, he is willing to engage constructively with the union.
He said: "I'm disappointed but I also accept the ballot and I will be working on the request made by the INTO in their initial correspondence to me, that is to engage constructively.
"That will be my messaging to the INTO that I'll be looking to engage constructively with them."