The honeymoon is well and truly over for Estelle Morris. This year’s teacher conferences will show how far school staff have lost confidence in her and the Government.

Workload will dominate the classroom unions’ conferences, with a joint motion threatening industrial action if the Government fails to fund reforms to teachers’ working conditions. The threat comes as the two heads’

unions are preparing for a ballot on industrial action over performance-related pay.

This is the second year running that a joint motion has gone to the classroom union conferences on workload.

It says teachers will refuse to work more than a 35-hour week if ministers fail to provide cash to cut workload in the Comprehensive Spending Review, outlining Government three-year spending plans.

The motion is backed by the National Union of Teachers, the National Association of Schoolmasters Union of Women Teachers, and the Association of Teachers and Lecturers, which meets next week.

Chancellor Gordon Brown has warned ministers, including Ms Morris, that their spending plans would have to be trimmed.

The unions did not say how much they hope to secure from the Treasury. Employers estimate it will cost pound;800 million for radical moves which include recruiting thousands more teachers and support staff.

The conferences of the three classroom unions, all in the TUC, come as relations between the union movement and Government hit an all-time low. John Monks, the TUC general secretary, recently made an unprecedented attack on Tony Blair over workers’ rights.

Until last week’s NUT strike over London allowances, teaching unions believed they could have a dialogue with the Government over workload. Now they are losing patience.

The threat of action comes as heads are offering their own solution to the workload problem. The National Association of Head Teachers and the Secondary Heads Association have lodged a joint submission to the School Teachers’ Review Body urging a reduction in the amount of “directed time” for teachers (the amount of time heads tell them to work) and a weekly limit of 21 hours’ teaching (see story below, right).

They are pressing for an annual limit on cover of 38 hours and said heads must have regard to the annual expectation that teachers will work 1,710 hours.

Effectively, this would give teachers a 45-hour week, although it would not satisfy the classroom unions’ demand that any limit should be written in the contract.

But it is a compromise that may well prove attractive to the Government. At present, primary teachers work an average 53-hour week and secondary teachers 51.

The submission coincides with proposed joint industrial action over pay. Ms Morris may dismiss last week’s NUT strike that closed more than 1,500 schools as the work of “wreckers” but it could be less easy for her to demonise heads, even though the action could affect every state school in England and Wales.

David Hart, general secretary of the NAHT, said: “The Government can’t sweep this to one side like a one-day strike in London.”

Performance pay dominated debate at heads’ conferences last week as delegates accused ministers of placing schools in an impossible position by introducing a system without proper funding.

Members of the NAHT and SHA say they have enough money to pay only half of the 200,000 who have crossed the threshold the pound;1,000 increases.

Heads say they will refuse even to assess staff until extra money is found. But the NASUWT believes heads should go ahead and assess post-threshold teachers and put them forward for the pay rise, thus exposing any shortfall in funding.

“Then you can take the moral high ground,” said general secretary Nigel de Gruchy. “David Blunkett repeatedly led people to believe that pound;31,000 would be available to good classroom teachers, but he never actually said it would be funded.”

The ATL is backing calls for full funding of post-threshold rises. The Government will be nervous that an upsurge in union militancy could hit its image in education. Ministers will argue that there are more teachers in schools, more money than ever and that it has made workload its priority.