The Labour party pledged this week to cut class sizes by putting thousands of extra teachers into infant schools, but has admitted this will take several years to achieve.

A start would be made on reducing class sizes for five, six and seven-year-olds in the first year of a Labour government, said a party spokesman. “The important thing is that a timetable has been set.”

Labour leader Tony Blair used his speech at the annual conference in Brighton to announce that the class-size money would come from the annual Pounds 104 million spent by the Government on assisted places in independent schools for bright children from low-income families. The party is committed to phasing out the Assisted Places scheme over the period it takes those in the system to complete their education.

Mr Blair’s promise to cut class sizes for five, six and seven-year-olds to under 30 has raised the stakes in the battle over Government spending policies. It also coincided with an opinion poll showing overwhelming parental support for smaller classes.

The Harris poll of just over 1,000 people, carried out for the Association of Teachers and Lecturers, found that 82 per cent believe large class sizes are threatening the quality of children’s education. An even larger proportion, 89 per cent, believe no primary-school child should be taught in a class of more than 30.

According to calculations made by the National Foundation for Educational Research, an additional 2,300 teachers would be needed to bring all classes of five, six and seven-years-olds to below 30. Their salaries would add around Pounds 60 million to the teachers’ pay bill.

But according to official Government figures the actual savings in the first year after the abolition of the Assisted Places scheme would be a maximum of Pounds 18.5 million.

The other problem for a Labour government looking for immediate cash savings is that it could not stop children taking up assisted places until it had amended the 1980 Education Act in the Commons. The present regulations require the independent schools in the scheme to be given three years’ notice of any Government desire to end the scheme.

Given the time it takes to legislate and the fact that in the first year less than a third of the money needed would be released, it could be three or four years before savings could pay for a cap on class sizes for younger children.

The front-bench education team argues that there will be money to make a start on reducing class sizes. The prospect of being able to make such a commitment has been under consideration for some months. The NFER was asked in June to draw up an estimate of costs.

Shadow education secretary David Blunkett and his team have been impressed by the Student Teacher Achievement Ratio (STAR) project in Tennessee that suggests the performance of younger children improves when they are taught in classes of fewer than 20. The task of ensuring classes are kept below 30 is likely to be left to the local education authorities - Labour is not at the moment planning to introduce legislation.

The detail of the mechanism by which local authorities would receive money that could only be spent on reducing class sizes has yet to be filled in. A Labour government could provide the money through the existing programme for funding priority schemes, the Grants for Education, Support and Training. Local management of school schemes could also be re-drafted.

* Backbench Tory MPs say teachers should not be singled out for special treatment in the next pay round and any award which exceeds the Government’s public-sector spending limit, likely to be around 0.5 per cent, should be met by local education authorities.

However, the MPs also said that extra money should be found for schools.