The NOP poll, commissioned by the National Association of Schoolmasters Union of Women Teachers, puts Labour ahead on 52 per cent, followed by the Liberal Democrats (27 per cent), with the Conservatives trailing in third place on 17 per cent.

When teachers were asked which party has the best education policies, however, 29 per cent said Labour, 28 per cent said Lib Dems, 8 per cent Conservative, 19 per cent said none and 16 per cent did not know.

In 1992, 43 per cent of teachers thought Labour’s education policies were best compared with 12 per cent for the Lib Dems and 8 per cent for the Conservatives.

Nigel de Gruchy, NASUWT general secretary, said: “The shift in favour of Liberal Democrat education policies could well be a result of Labour’s constant, and sometimes confusing, shifts of policy in recent times.”

If elected, the Lib Dems, would raise income tax by a penny and use the money to increase spending in schools.

The poll also shows clear support for a pay review body for teachers (84 per cent), despite the present School Teachers’ Review Body having phased teachers’ pay for the past two years. A General Teaching Council was favoured by 58 per cent of the sample.

More than nine out of 10 teachers said they were very or fairly frustrated by their workloads, and 88 per cent said they were very frustrated by public criticism of teachers. Almost half of those interviewed said they had considered leaving the profession in the past five years. This, however, has dropped from 60 per cent in 1992.

Members of the NASUWT and National Union of Teachers had above-average levels of Labour support, while the Association of Teachers and Lecturers had a high figure for the Lib Dems (36 per cent).

A fully representative sample of 835 teachers was interviewed in England and Wales between March 13 and March 21.

An ICM poll for the NUT four weeks ago showed that among teachers, 59 per cent supported Labour, 21 per cent the Lib Dems, 15 per cent Conservative and 5 per cent other parties.