Head teachers have voted to stage a ballot on whether to strike over planned changes to their pensions.
A motion to "take all action necessary to defend pensions up to and including balloting on industrial action" was passed by 99.6% of delegates at the National Association of Head Teachers (NAHT) during their annual conference in Brighton.
The 28,000 members of the union will now be balloted on the motion.
The NAHT believes changes proposed by a review led by Lord Hutton will damage motivation and morale.
The full text of the motion read: "Conference calls upon National Executive to take all action necessary to defend pensions up to and including balloting on industrial action, in opposition to the changes proposed by the Hutton inquiry, as they will reduce existing and worsen future retirement benefits for the teaching profession and the public sector as a whole.
"NAHT believes that the proposed changes will seriously damage motivation and morale, exacerbating the already serious problems of recruitment and retention of school leaders."
NAHT member Brian McNutt described the Government's approached as "disaster politics".
He told the conference Chancellor George Osborne was from the "Arthur Daley school of economics".
David Fann, national executive member, said: "We're going to pay more, work longer and get less."
