Estelle Morris’s threat to boycott future union conferences if she gets a rough ride this time is likely to cut little ice with delegates.

This week, the normally moderate Association of Teachers and Lecturers unanimously approved a motion threatening industrial action if the Government fails to cut teacher workload.

The motion, which reaffirms last year’s joint resolution calling for a McCrone-style agreement south of the border, has been drawn up with the two other major classroom unions, who are expected to follow suit at their conferences.

While welcoming the Government’s intention to reduce the “excessive” burdens on teachers, it calls on the Treasury to fund the reforms properly and to continue joint working on the roles and responsibilities of teachers and staff.

Any new arrangements for cutting workload must be achieved through agreement with teaching and support staff unions, not by imposition, the motion warns.

Given this, Ms Morris’s move last week to veto a central plank of the unions’ strategy for tackling workload could hardly have been better timed to create a major row.

In a letter to the School Teachers’ Review Body, released to union leaders last Friday, Ms Morris ruled out a limit on teachers’ classroom time. Instead she suggests guaranteed “professional time” for marking and preparation.

National Union of Teachers general secretary Doug McAvoy said: “That’s absurd. If teachers are to be given time for marking and preparation, there also has to be a limit on the time they spend teaching.” Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers, said: “But when will it (guaranteed professional time) become available? 7pm?”

John Atkins, the consultant whose report provided the basis for the unions’

workload reduction proposals, said: “The truth is that... many teachers are already at or near 100 per cent class contact. They cannot even theoretically teach any more than they do.”

National Union of Teachers’ left-wingers will also press the leadership for further London strikes, at the NUT conference in Bournemouth, which starts tomorrow. They want cost-of-living allowances in the capital to rise from pound;3,000 to pound;4,000 from September.

The one-day strike earlier this month might ensure an easier time again this year for the NUT leadership, left-wingers predict. Ian Murch, executive member for west Yorkshire, said: “It has deflected a lot of criticism.”

Results of elections to the union’s executive, to be announced at the conference, are likely to provide further good cheer for Mr McAvoy, as he gains a supporter.

Meanwhile, the NASUWT, whose conference starts in Scarborough on Monday, threatens industrial action if LEAs go ahead with plans for a six-term year. Mr de Gruchy says the Local Government Association proposals represent “a significant amount of change for no great benefit”.