More than 100 prep schools could be forced to close because of a government-mandated hike in pension contributions next year, according to a leading figure from the independent sector.

Chris King, chief executive of the Independent Association of Prep Schools (IAPS), said he had written to treasury minister Liz Truss warning that up to 25,000 children could be left without a school next term.

“I think the impact might well close over 100 schools in membership of IAPS,” he told Tes.

“The vast majority of IAPS member schools are relatively small institutions. Many of them have 100, not much more than 200 pupils.

“These kinds of schools operate with pretty much break-even budgets, they don’t generate huge surpluses. But they often are really embedded in their local community – they serve the local community, they are specialists in what they provide.

"These schools really have nowhere to turn with such swingeing hikes other than to raise their fees."

Schools were told last month that they must increase contributions to the Teacher’s Pension Scheme by more than 40 per cent from next year after a government review into public sector pension schemes.

Bewildered headteachers reacted with shock to the announcement that they must increase employer contributions to 23.6 per cent from September 2019, up from 16.48 per cent now.

Two thousand heads marched on Downing Street last week to call for a reversal of the real-term cuts in funding that schools have faced over the past eight years.

A Treasury source said the government has offered to “help” maintained schools and academies meet the additional costs.

But King pointed out that independent schools would get no such aid – and mass closures of fee-paying schools as early as the end of this academic year would have a swift knock-on effect for the state sector.

"The review of the pension contribution appears to have been an exercise carried out with blinkers on,” he said.

“This has the potential to have a significant impact across the education sector… The reality is in terms of costs, for every three teachers you employ you’re actually paying for four, and that’s not sustainable.”