The INTO has voted by a narrow margin against a motion calling for a rejection of the public service pay deal.
The emergency motion was rejected by a margin of just four votes - 308 to 304 - in a session held in private.
The vote underlines the deep divisions among teaching unions about the deal.
Last week, the INTO executive backed the deal and recommended its acceptance by members in the forthcoming ballot of members. This recommendation will now go to members after today’s vote.
The three teacher unions are split on the deal . While the INTO has backed it, it has been opposed by the ASTI and the TUI.
Earlier, Minister for Education and Skills Mary Coughlan faced some heckles and booing from a minority of delegates at the INTO conference.
In her first address in the education portfolio, she warned that the State will have less to spend on public services for the foreseeable future. There were "no easy options and no easy decisions" in working to safeguard the economy and the banking system, she said.
Ms Coughlan said the Government viewed the proposed deal on public service reform and pay as a "reasonable basis to move forward". But she had no intention of interfering with internal union debates on the issue.
The Minister acknowledged it was not possible to shelter education completely from any further spending cuts.
“For me to do so would be dishonest, given that the bulk of public expenditure is accounted for by health, education and welfare,” she said. But she said the revised Programme for Government – which promised no further increase in class size – “underlines the Government commitment to investment in this key area.”
The Minister's speech was punctuated by frequent heckling and booing from the floor. About 100 delegates held up placards critical of the Government's economic policies.
She warned against the creation of "dangerous divisions" in Irish society.
"The phoney division between public sector Ireland and private sector Ireland so regurgitated by the commentariat must be dispelled. The reality is that each is reliant on the other and that this is a difficult time for everyone living in this country …These unhelpful divisions can damage our shared sense of purpose and solidarity.”
In her address, new INTO general secretary, Sheila Nunan said the education system will continue to be grossly under funded while the architects of our economic catastrophe are free to play golf in Spain or remain in hiding in the US.
She said the citizens of State - who had to cope with the banking crisis - were being asked to believe that cutting salaries, suppressing recruitment and promotions, threatening pensions and annihilating morale of decent hardworking men and women will solve our economic woes.
The light touch regulation of the banks was, she said, a euphemism for letting the lunatics run the asylum. “The education system will remain under funded and our classrooms overcrowded. Child poverty will increase and ordinary working men and women face the challenge of making ends while the guilty are still not brought to justice.”
She also congratulated the new Minister on her appointment. “If you don’t believe half the things you’ve heard about teachers we won’t believe half the things we’ve heard about you,” Ms Nunan said.
Ms Nunan, in her first address as general secretary, accused the Government of “cataclysmic mismanagement” of the Irish economy.
“This Government has mortgaged the future of Irish children,” she said. “Six years from the centenary of 1916, that is some betrayal of their heroic struggle for independence of which the trade union movement of the time was a part. …James Connolly must be turning in his grave.”
In contrast, she said teachers are ambitious for the success of primary education, for their pupils, for this economy and for this country. “They need no lectures in patriotism. They don’t have to be told to don the green jersey,” she said. They know the contribution primary education makes and can continue to make to national recovery.”