Education Secretary Alan Johnson has provoked fury among teachers after refusing to allow a review of their pay.
Unions had called for fresh talks over the pay rise teachers are set to receive in September after inflation soared beyond the agreed level to trigger a review.
The independent group which oversees teachers' national pay talks also called on Mr Johnson to allow it to conduct a review - but the minister refused.
The National Union of Teachers (NUT) condemned Mr Johnson, who is a front-runner to become the next deputy leader of the Labour Party, for failing to keep his word.
NUT general secretary Steve Sinnott said: "This is a breach of honour. Teachers have been let down. Teachers had been promised the possibility of their increase being reassessed. Instead of that, they face a cut in pay in real terms of between £300 and £600 just in the year from September.
"Teachers have already suffered pay cuts in real terms over the past few years. This will not go down well in classrooms across the country."
He said the NUT will be asking the TUC to convene a meeting with other teachers' unions to decide what steps to take in response to Mr Johnson's decision.
The GMB union called for co-ordinated industrial action across the public sector against Government pay restraint.
The union said that, with disputes now spreading across the NHS, local government, civil service and education, it was clear that Gordon Brown faced a "showdown" when he takes over as prime minister later this month.
National officer, Brian Strutton, said: "Gordon Brown is setting sub-inflation caps on negotiators and refusing to accept review body recommendations. As a result, nearly five million public sector workers face pay cuts in real terms and this is simply not acceptable. The Government is deliberately picking a fight with public sector workers and we should respond with a co-ordinated campaign of industrial action."
