The largest teachers’ union is preparing to broaden its campaign of industrial action with fresh strikes in protest against cuts to school budgets.

The annual conference of the National Union of Teachers will vote tomorrow on a call to ballot members for another round of strikes, opening up a new front in a long-running dispute over pay, pensions and working hours.

Christine Blower, the union’s general-secretary, said that she would lay plans for a national strike if a new government did not commit to at least maintain school spending levels.

NUT members staged a national strike in July last year.