General secretary of secondary teachers' union ASTI Pat King has claimed his members have students at heart as it looks set for a major confrontation with the Government over its rejection of the Haddington Road Agreement.

The Government has insisted there will be no renegotiation of the agreement on public service pay despite Friday’s decision of the ASTI.

The standing committee of the 17,000-strong union meets tomorrow to consider the nature of any action in the wake of the ballot result but disruption in secondary schools is likely before Christmas.

Minister for Education Ruairí Quinn has expressed his disappointment at the union's decision. He is expected this week to discuss the issue with Minister for Public Expenditure and Reform Brendan Howlin and other Cabinet colleagues.

Speaking on RTÉ’s This Week, Mr King said the fabric of schools had been disintegrating for the past five years. “The staffing cuts, loss of language supports, loss of resource supports, larger classes. And now teachers are being asked to do extra hours and extra work and they’re saying no.”

He could “guarantee parents that teachers have students needs at heart” and suggested that it was “more than likely that the target will be those commitments we made in Croke Park. That was to last until 2014 and guaranteed no pay cuts. If the Government has torn up that agreement, we will have to withdraw our commitment to do extra hours.”

Mr King hoped it would not come to a strike but administration hours would be disrupted. It “will have some impact, but not directly on students. Teachers haven’t time to deal with everything and are being asked to do more,” he said.

The Teachers’ Union of Ireland decision to back the Haddington Road agreement leaves the ASTI in an isolated position. Primary teachers have already accepted the deal. Asked about the TUI’s approval, Mr King said “everyone is entitled to make their own decisions .”