Education Secretary Gillian Keegan is under pressure to publish pay proposals for teachers or risk school strikes dragging on.
As tens of thousands of teachers prepare to walk out tomorrow, education unions warned Ms Keegan that the failure to get round the table could deepen the bitter dispute over pay.
Schools across England will face disruption on Wednesday and Friday as members of the National Education Union (NEU) down tools in the latest of a series of nationwide strikes.
All the major teaching unions are conducting fresh ballots on industrial action, raising the threat of further strikes in the autumn term.
The unions have already rejected a £1,000 one-off payment for 2022/23 and an average 4.5% rise for staff next year.
Ms Keegan kicked the decision to the Government-appointed pay review body, which has reportedly recommended a 6.5% wage hike.
But the Department for Education (DfE) has refused to publish the advice amid mounting speculation ministers could offer less than the amount recommended by pay review bosses.
In a joint letter to Ms Keegan, the leaders of the TUC, NEU, NASUWT, NAHT and ASCL unions said the hold-up is causing "anxiety" in schools and "frustrating headteachers" who need to plan budgets.
The unions said: "There is no good reason for any delay in their publication.
"Further delay is leading to continuing anxiety across all schools and frustrating head teachers and school leaders' ability to plan and manage already difficult budgets for the forthcoming school year."
It added: "It is in everyone's interest that the current dispute is brought to a swift resolution. The ball is firmly in government's court.
"We urge you to publish the (pay review) recommendations without delay and engage immediately in meaningful negotiations with unions."
A DfE spokesperson said: "Any strike action is hugely damaging. We have made a fair and reasonable pay offer to teachers, recognising their incredible work and commitment.
"Thousands of schools received significant additional funding as part of the extra £2 billion of investment we are providing both this year and next.
"As a result, school funding will be at its highest level in history next year, as measured by the IFS (Institute for Fiscal Studies)."
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