The education minister Stephen Timms entered the lion's den when he addressed the annual conference of the NASUWT union.

The union had earlier warned that government plans to create teacher's assistants could lead to a "mum's army" of unqualified staff entering the classroom.

Whilst Timms insisted that the new assistants will play no formal teaching role, the union believes they will damage the quality of education and hit morale in the classroom.

"We...need to look at types of pupil supervision that do not nee to be done by teachers...and how, just as learning support assistants have made such a big contribution to special needs teaching, so we can make better use of support staff, given the appropriate training, to improve the teaching function itself," the minister said.

"Not instead of additional teachers but as well as. Ensuring that more of teachers' time is spent on those activities that really need professional, expert input."

The union has warned that the new approach amounts to a "disastrous scenario" where children were left under the sole charge of unqualified support staff.

The move comes as teachers prepare to vote on industrial action in a move which could further sour relations between frontline teaching staff and the government.

Working Week

At the annual general meeting of the National Union of Teachers, which is also took place on Tuesday, members voted on industrial action over their demands for a 35-hour maximum working week.

The vote, which is also likely to win the backing of the NASUWT, will set teachers on a collision course with the education secretary Estelle Morris.

Last week the Association of Teachers and Lecturers backed a motion threatening action over the excessive workload of teaching staff.

Whilst strike action seems unlikely, teachers appear set to agree to a boycott of paperwork in protest at the government's failure to address their concerns over workload.

Potty

Morris, who was heckled by teachers when she addressed the conference at the weekend, has dismissed the proposed action as "potty".

"You can't run a school with teachers clocking on and clocking off - it has to be more subtle than that," she said.

Teachers work an average of 53 hours a week, according to independent research.

Hopes of a compromise, however, were increased when the education secretary said that 20 per cent of teachers' current work could be transferred to other staff.

It was suggested on Tuesday that the government was preparing to offer teachers an extra five hours preparation time in school hours.

Timms dismissed the reports as "speculation" and warned that the threat of strike action was "irresponsible and wholly premature".

The latest spat between the unions and the government comes amid heightened tensions across the key public services.

A survey of nurses showed that the majority are prepared to take industrial action in protest over pay and working conditions.

According to Nursing Times, 94 per cent of its readers said they would be willing to take part in industrial action. Fewer than six per cent of those polled said they would never consider strike action.