They will seek a radical review of the way schools are funded in an attempt to end years of cuts which have led to widespread redundancies and booming class sizes, and left buildings and supply of books and equipment at crisis point.

The National Association of Head Teachers wants assurances from the Government that by the end of its first five-year term of office a higher proportion of the nation’s Gross Domestic Product would be devoted to education.

And it said that it did not expect the Government to stop at cutting classes to 30 or fewer for every five, six and seven-year-old - it expects moves towards reducing class size at all key stages as well as cash to start clearing the Pounds 3.2 billion backlog of repairs and maintenance.

David Blunkett, the Education and Employment Secretary, will address the NAHT conference today in his first public appearance at a teacher union conference since the election. He will be told the Government must come up with more money if he is to save schools from deterioration.

The union also wants public acknowledgement from ministers who have pledged to improve pupil performance that standards have not fallen.

The NAHT spoke out just a week after the Government unveiled a “list of shame” of 18 failing schools, given until September to improve, and days after Stephen Byers, the standards minister, sought the help of local authorities and unions to get rid of bad teachers more quickly.

Delegates were told that teachers were breaking under the pressure of underfunding and workload in buildings that were a national disgrace. Headteachers were working way beyond EC directives on hours - in some cases by almost 10 hours a week. The number of heads and deputies quitting either early or on health grounds has soared from 693 in 56 local authorities in England in 199596 to 1,087 in the same LEAs the following year.

Early retirements were highest in London and the new unitary authorities, while the capital also headed the league table of retirements on health grounds.

David Hart, general secretary, said there had been a catastrophic increase in the number of top people leaving well before their anticipated retirement date, and he warned that many schools would have only acting heads in post next year.

“This cannot help the drive for higher standards the new Government is spearheading,” he added.

A paper to be presented to the conference today says: “The nation can no longer afford, and never deserved, education on the cheap. We do not expect revolution, but we do hope for evolution. This Government must be prepared to work with us in the pursuit of common goals.”

Both the Department for Education and Employment and the Funding Agency for Schools - the quango which administers finance for the grant-maintained sector - have been working on a national funding formula.

Three months ago Peter Kilfoyle, then shadow minister for schools, said it would be “massively disruptive, costly and over-regulatory”.

The NAHT said a national funding formula would not automatically provide more cash, but would provide clear evidence of the need and a simple mechanism for distribution as funds became available.