And the teachers' union which commissioned the survey says that "woefully inadequate" levels of pay are discouraging new recruits.

A rising population of school-age children and a shortage of young people coming into teaching is leading towards a recruitment crisis in England and Wales, say researchers Professor Alan Smithers and Dr Pamela Robinson of Liverpool University.

Teachers' unions say better pay is the key to recruitment

While applications for teaching have been boosted by the government's offer of cash incentives for shortage subjects, the researchers say that the age profile of teaching means that there are still recruitment problems ahead.

Only 17% of teachers are under 30, while 20% are aged over 50 - figures which the researchers say shows that the teaching profession is "not renewing itself".

The prospect of more teachers retiring than are being recruited is against the background of a projected additional 300,000 secondary school pupils in the next six years.

The research, commissioned by the National Union of Teachers, says that the long-term impact of the "golden hello" cash incentives had not yet been determined.

'Substantial' pay rise needed

The publication of the report coincides with a joint teachers' union submission to the profession's pay review body calling for a "substantial" improvement in teachers' pay.

"While the economy is buoyant, young people are rejecting the stresses and strains of teaching for more financially rewarding employment which offers them greater career development and far better working conditions than is currently the case for teachers," said Doug McAvoy, the General Secretary of the NUT.