Head teachers have threatened to take industrial action if talks on workload fail to produce results.

Heads say they need more time away from the classroom for their management duties and they want more administrative staff in schools.

Delegates at the National Association of Head Teachers passed a motion to ballot for action at the end of the year if current discussions with the government and employers failed to produce better working conditions.

The move by the NAHT would be the first time the union had resorted to national industrial action.

General secretary of the NAHT, David Hart, said an incoming government had to understand that the patience of heads and deputies was "well nigh exhausted".

Warning shot

"This is firing a warning shot across the bows of any new government," Mr Hart warned.

It was not just the unions which took part in industrial action earlier this year which had serious concerns, he said.

The action could take the form of imposing a maximum working week or refusing to implement any government initiatives which would increase workload, Mr Hart said.

"There is no question of us doing anything to harm the education of pupils," he stressed.

Circus performers

The motion was proposed by Wigan head teacher, Dave Johnson, who compared head teachers to circus performers.

They marched to the drumbeat of Ofsted, trod the diplomatic tightrope and, like good jugglers, kept more and more objects in the air.

They were burdened by bureaucracy and initiatives, he said.

"We should be devoting our time, energy and expertise to the children we all care so much about."

Hugh Carey, who seconded the motion, said the burden of bureaucracy still hindered the effective management of schools.

"More and more is being delivered into schools with an expectation that it will be done," he told the conference.

'Enough is enough'

"There must come a time when our organisation says enough is enough."

Head teacher Margaret Evitts said heads should receive two salaries in recognition of the administrative work they did as there was not enough money to employ clerical support staff.

A review into teachers' workload is being conducted and will report to the teachers' pay review body in the autumn.

The NAHT will make its decision for or against industrial action depending on the pay review body's subsequent recommendations.