The Government has ordered an inquiry and the Department for Education (DfE) has apologised after it miscalculated its funding plans for the next academic year.

The DfE’s top official, permanent secretary Susan Acland-Hood, said in a letter to the Parliamentary Education Select Committee the number of pupils was underestimated, with a planned 2.7% increase per pupil for 2024/25 subsequently revised to 1.9%.

“We will therefore be issuing new NFF (National Funding Formula) allocations to correct that error while continuing to deliver, in full, the £59.6bn Core Schools Budget that has been promised,” the letter states.

Improvements have already been identified to ensure similar mistakes are not repeated in the future

“I apologise for this error. The Secretary of State has asked me to conduct a formal review of the quality assurance process surrounding the calculation of the NFF, with independent scrutiny.

“Improvements have already been identified to ensure similar mistakes are not repeated in the future.”

The NFF is the method the Government uses to decide how much money should be given to English state schools each year.

According to the BBC, the originally planned increase would have inflated the overall schools budget by £370 million.

Although the money for 2024/25 has not yet been paid out, Ms Acland-Hood said the DfE “recognise that the correction of this error will be difficult for local authorities and frustrating for some school leaders”.

She added: “We will work closely with school stakeholders, including unions, to communicate this change and support schools and local authorities.”

Paul Whiteman, general secretary of school leaders’ union NAHT, said: “Today’s announcement that the DfE has incorrectly calculated the national funding formula for 2024-25 speaks volumes about the chaos at the heart of government.

“School leaders will be rightly angry that basic accounting errors may force them to rethink already tight budgets as a result of the erroneous figures they were provided.

“Many may now have to revisit crucial decisions around staffing or support for pupils as budgets are reduced.

“Rushed announcements about half-baked policy initiatives, such as mobile phone bans or overhauling 16-18 education without any consultation with the sector, are worrying enough, but how can school leaders have confidence in headline grabbing policy developments if they can’t even trust their budget allocations.”

Daniel Kebede, general secretary of the National Education Union, called the error “shocking”.

In a post on X, formerly Twitter, late on Friday, he said: “On Wednesday, (Rishi) Sunak said he would prioritise education funding.

“Now I’ve just been called into a last-minute DfE meeting (5.30pm Friday), only to be informed that unplanned cuts are coming!”

He added: “We already have record class sizes and can’t recruit or retain teachers.

“Sunak must commit to stop school cuts.”

Shadow education secretary Bridget Phillipson said: “More Tory chaos, more uncertainty for schools and families struggling under the weight of thirteen years of cuts.

“Only Labour will drive the high and rising standards our children deserve.”