The cost of the national and regional schools commissioners has sky-rocketed, from just £4 million when the roles were established in 2014 to £26 million last year, Schools Week can reveal.

The price tag for the commissioners and their teams is expected to rise again for the current financial year, to an estimated £31.2 million, according to figures obtained through a freedom of information request.

Fears that the eight RSCs’ budgets would spiral out of control were raised in February last year, after the government revealed staff and administration costs had risen to more than £650,000 per region.

Schools minister Lord Nash confirmed that each of the eight commissioners was getting £520,000 a year to spend on salaries and expenses for between eight and 10 employees, on top of £40,000 for events and communication, and £100,000 to compensate employers of the leaders who sit on their headteacher boards.

Jonathan Crossley-Holland, education consultant and former director for children’s services at Sheffield City Council, said the increasing costs were evidence that the RSCs have become a middle tier of oversight for schools.

“These are enormous increases,” he said. “When Michael Gove announced the setting of RSCs in 2012 he was adamant that they were not a new middle tier. Clearly, this is what an RSC now is.

“What is very disappointing is that this has happened by stealth without a proper public debate about their role and how they can be held accountable locally.”

When questioned on the rising costs, a DfE spokesperson told Schools Week the increase was down to the RSC teams taking on more staff.

She said: “The increased costs reflect a restructure within the department in 2015/16 to ensure the wider work on academies was more aligned with the regional schools commissioners’ activity.

“As the number of academies and free schools has increased, the eight RSCs have recruited strong teams to support their work to provide effective oversight of schools and advise the national school commissioner and ministers.”

When the NSC and RSC roles were first established in July 2014, to oversee the growing numbers of academies across country, set-up and running costs came in at just £4.1 million. This funding came from the Department for Education’s existing budget and covered July 2014 to March 2015.

The combined costs of the NSC, at the time Frank Green, and the RSCs was similar for the financial year 2015-16, at £4.7 million of the DfE’s allocated funding, but the figure leapt to £26.3 million in 2016-17.

In June 2016 Schools Week reported that each RSC would now have two deputy directors, paid up to £95,000, and a further individual would be appointed to support new NSC Sir David Carter with his work.

Mary Bousted, joint general secretary of the National Education Union, said the climbing cost of the RSC network called into question whether it was “fit for purpose”.

She pointed out that the size of the regions managed by the RSCs and the rapid expansion of a number of MATs makes it a challenge to keep up with what is going on in each academy.

“At keys stage 4 we’ve got over 50 per cent of MATs underperforming, at key stage 2 its 50 per cent, and the RSCs don’t seem to be able to be effective in stopping the scandals which have rocked the system so badly,” she added.

“All this growth in the RSCs is a desperate attempt to try and get a handle on an increasingly incoherent and dysfunctional system.”