The DfE has admitted it does not know how many academy trusts are operating under funding agreements that completely relinquish public control of state school land.

The problem has been highlighted by the case of Durand Academy, where public assets then valued at £15 million were transferred to a separate organisation, Durand Education Trust, when the South London school became an academy in 2010.

Last November, the Commons Public Accounts Committee heard that while the school buildings had been returned to Lambeth Council after the Department for Education (DfE) terminated the academy’s funding agreement, Durand Education Trust maintained that it still owned land on the school site and accommodation and a leisure centre that had been built there.

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The government is currently in the midst of a lengthy legal battle to try and win back control of the previously publicly owned land.

Now an academies lawyer has warned that although the DfE has tightened the rules in recent years to prevent this happening again, many older academy trusts are still operating under historic funding agreements that could cause the same problem.

Some agreements have avoided the issue by allowing local authorities to retain the freehold of school land and lease it to academy trusts.

But Matthew Wolton, a lawyer at Knights plc, said Durand-style problems could be repeated in cases where the land was not owned by the church or a local authority.

He said there were older such academy funding agreements that also lacked clauses giving the DfE the right to acquire the land at no cost if and when the funding agreement was terminated.

“The risk that Durand has identified is that there are instances where land used for schools is not within the control of the Department for Education,” he said.

Mr Wolton said that the number of older funding agreements that could give rise to problems with the land “may well be three figures, but I don’t think it will run into the hundreds and hundreds”.

He had come across “perhaps two or three handfuls, a number of scenarios where you are dealing with charitable foundations and bodies which are not technically controlled by the DfE and you could have another problem like [Durand]”, he said.

When Tes asked the DfE how many such historic agreements are still in place, it said: “We don’t have that information easily to hand.”

The department added that because the issue does not affect the revenue funding of academies, it is “not information we keep in an easily navigable way”, and it would need to inspect the funding agreement of each academy or multi-academy trust to find this information.

Mary Bousted, joint general secretary of the NEU teaching union, said: “Unfortunately, it’s part of a well-trod path of the DfE not having the information, nor the information systems, to know which way is up when it comes to the public resources it has, in effect, privatised.

“It’s further evidence of an academisation programme that was done at breakneck speed without any safeguards being put in place to ensure that national assets were used for the nation’s good.”