Second and third level teachers have warned that any allowance cuts will be a breach of the Croke Park Agreement.
The issue is dominating the opening day of the Teachers Union of Ireland (TUI) annual congress in Wexford.
The TUI warned that if the Government departs from the commitments not to cut pay or make teachers redundant, "all bets are off".
The union's new general secretary John MacGabhann said his members would not stand for any deviation from the terms and conditions agreed.
"Allowances are an intrinsic, indivisible part of the pay of teachers," he said.
"Teachers' pay is protected by the Croke Park Agreement.
"A cut in teachers' pay would be a breach of the Croke Park Agreement, with all the consequence that would bring."
The agreement, between the Government and public sector workers, was made in 2010. The former promised no further reductions in workers’ pay rates from 2010 to 2014 and no compulsory redundancies.
In exchange, public servants agreed to be flexible in their work to change the way the public service runs, to help improve how it works while reducing costs.