Statistics from Education Data Surveys showed that 2,177 primary headships and 2,400 deputy headships were advertised last year, representing one senior vacancy in almost 10 per cent of all primaries in England and Wales.

The report’s author John Howson claimed that many were having difficulties finding replacements, even though some schools outside London were offering up to pound;50,000 a year for headships.

An NUT spokeswoman said the crisis was “spread right across the board”, despite an apparent belief in the national news media that the primary sector is faring well. She added that the shortage was set to worsen as new teachers failed to enter or stay in the profession, and the number of experienced, promotable staff dwindled.

One side-effect in some areas has been a shortage of supply teachers. Primary heads sa that good supply staff are now working on contracts of a term or longer, many covering unfilled permanent vacancies. As a result, specialists in larger primaries who don’t have their own classes are taking classes for whom no full-time replacement can be found. While this may be a short-term solution, the effects on special needs groups, extra maths sets and managerial overload soon become added burdens.

Such solutions may also be contrary to staff contracts, especially if governors and heads had plenty of warning of the vacancy, as in the case of maternity leave, but had been unable to find a suitable replacement.

Questionnaires have been sent out by NUT and NASUWT in London, Doncaster and Leicester asking teachers how serious the crisis is in their schools.

Meanwhile, the National Employers Organisation for School Teachers has threatened to dock pound;100 a day from the pay of those who take industrial action. Teachers’ unions have advised members not to take action without contacting them first.