In an increasingly bitter dispute over teachers’ working conditions, Chris Keates, the general secretary of the National Association of Schoolmasters and Union of Women Teachers, pledged to “out” those head teachers who have done nothing towards implementing the national workforce reform agreement.

Several head teachers say that they cannot implement the reforms because of a lack of funding and have called on the Government to provide them with money to hire extra staff.

From September, all teachers will be entitled to a half-day free in the school timetable for preparing lessons and for marking.

Ruth Kelly, the Education Secretary, said last week that teachers should sue schools if they are not given time off and insisted that head teachers would be breaking the law. This month, the National Association of Head Teachers pulled out of the agreement, complaining of a lack of enough funds.

Ms Keates, who believes the agreement is the best deal for teachers in decades, calculates that as many as one in ten head teachers may seek to break the law. Speaking at the association’s annual conference in Brighton, she said that should they do so, they risked losing their jobs.

“They must recognise they would face disciplinary procedures and that could mean them being sacked,” she said.

From next week, the association — England’s second-largest teaching union with 223,000 members — will send out hundreds of letters telling governing bodies, local education authorities and head teachers that those who fail to implement the reforms could also face being sued.

“If a teacher went into a school and simply said: ‘I’m not obeying the law of the land and not following the contract,’ the governors and the local education authority would be exhorting the head teacher to take the harshest teacher discipline procedures,” she said, adding: “Breaches of the working time regulations and excessive hours may give rise to claims of negligence in civil proceedings claiming damages for occupational stress .”

Last week members of the Association of Teachers and Lecturers threatened to strike if their rights were not met by schools. Teachers will receive their autumn timetables shortly after returning to school from the Easter holidays.

The Government says that the agreement was prompted by complaints over the heavy teacher workload, which was having affecting recruitment, retention and teacher morale.

The workforce reform agreement, signed by most parties two years ago and to have been phased in over three years, allows additional cover for absent teachers, teaching assistants to take over administrative tasks and for 10 per cent of the timetable to be set aside for PPA — planning, preparation and assessment.

The National Union of Teachers refused to sign the agreement over concerns about unqualified teaching assistants replacing staff, but the reforms are binding on all state primary and secondary schools in England and Wales.

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