By Justin Parkinson BBC News Online education staff at the NAHT conference

The Workload Agreement tries to cut administration for teachers

Under the agreement, signed last year, tasks like register-reading and photocopying are taken away from teachers.

But the National Association of Head Teachers heard the scheme had been under-funded.

Its annual conference in Cardiff voted to "withdraw" unless more money was

made available.

Heads say they have been forced to sack support staff - the very ones taking over teachers' old administrative tasks - because the workload agreement is so expensive.

It promises to free teachers from 21 tasks, including collecting money and putting up classroom displays, giving them more time for tuition.

From next September, they will get 10% of their time devoted to "planning, preparation and assessment", according to the agreement's terms.

'The figures don't stack up'

Paul Summers, head teacher of Nyland School, Swindon, said: "Where are the resources to support its implementation and maintenance."

He added: "The figures just don't stack up. In Swindon, staff are already being made redundant. We also have schools with deficit budgets.

"Many more will be in deficit, just to meet current levels of provision.

"The workload agreement is a flagship government policy and fundamental to the health of our profession.

"But how can we be expected to carry out our moral responsibility as heads without more money?"

The government has described the agreement as a "remodelling of the [teaching] profession", pledging �1bn for its implementation.

'Cheap labour'

However, the National Union of Teachers has refused to sign up, saying that giving some teachers' tasks to classroom assistants amounts to "cheap labour".

A Times Educational Supplement survey of 500 teachers in January found 45% had had no extra time freed up as a result of the agreement.

Schools reported budget deficits of up to �500,000 last year, amid a controversy about whether extra government funding was reaching head teachers.

Bridget Handby, head of Burton Agnes Primary School in Driffield, Yorkshire, told the NAHT conference: "We are deeply, deeply worried about the 10% PPA (planning, preparation and assessment) time that we feel our staff deserve.

"We really feel we need to put pressure on the government to realise just how important the issue is."

Mike Welsh, head of Goddard Primary School, Swindon, added: "We are going in the wrong direction due to a lack of resources."

The NAHT's general secretary, David Hart, called for a later deadline - 1 April next year - to set the government to improve funding.

This, he said, would make any demands make the union's demands more "deliverable".

Other delegates had called for a deadline of 31 August this year to be set.

But the conference eventually voted for a compromise date of 31 December this year.

'Untenable and hypocritical'

There was a furious response later from Chris Keates, deputy general secretary of the NASUWT teachers' union.

"The truth is that some heads have finally read the agreement's provisions and realised the days of managing teachers by exploiting a vague and all-embracing contract have gone forever," she said.

"They need to come to terms, very quickly, with the fact that these changes are statutory. They are neither voluntary nor optional."

She added: "If press reports are to be believed, I am appalled that the NAHT has apparently resorted to making gratuitous insults about teachers seeking a minimal working week to shore up the increasingly arrogant, untenable and hypocritical position of the NAHT on this issue."