Labour asked the National Foundation for Educational Research to produce a revised estimate to back up its pledge to reduce class sizes. The promise, originally made at last autumn's annual conference, was reiterated in last week's "road to the manifesto" document.
The NFER has put the cost at Pounds 68 million. The cost of the scheme, which provides public money to send less wealthy children to independent schools, was Pounds 104m for 1994-95.
Last autumn, John Major announced that the Government would double the number of existing assisted places to 68,000. This year, 3,910 places have been created, pushing the cost of the scheme up to Pounds 118m. The Department for Education and Employment says that this figure would rise to Pounds 141m for 1997-98.
If Labour wins the next election, it would, therefore, have a substantial amount left over once class sizes had been cut. A Labour spokesman said that it would take about three years to phase out the scheme and fulfil the pledge on class size, and the rest of the money would be used "to raise standards in primary schools".
The NFER's figure of Pounds 68m to reduce class sizes contrasts dramatically with an estimate of Pounds 170m made for the Government by the Office for Standards in Education last November. OFSTED argued that the higher figure included increased accommodation and transport costs.
But the NFER said that "some readjustment would be needed for transport and accommodation costs, but not to such a degree". Ralph Tabberer, NFER assistant director of research, pointed out that, in Staffordshire, where a project to reduce class sizes in 31 of the local education authority's most disadvantaged schools is under way, "no significant transport and accommodation adjustments have been necessary".
Labour argued that OFSTED's estimate was "pulled out of a hat in order to distract attention from the fact that their report accepted the premise that class sizes do make a difference in the early years".
Latest government figures indicate that one third of all primary children are now being taught in classes of more than 30, an increase of 9 per cent on last year.