A further £23m remains unclaimed in the Funds in Court account - with some outstanding balances dating back to the 1700s, according to the National Audit Office.

The FiC account holds money for people who are mentally incapacitated or children who have their financial affairs controlled by the courts.

It also holds assets of people who have paid in money to the courts ahead of a legal battle which they might lose.

However, the NAO said some £33m lay unclaimed in the account and £9.8m was "unattributed to individual cases".

'Mismanagement'

The report, written by Auditor General Sir John Bourn, said: "A key function CFO is the custody of money or assets on behalf of others.

"The CFO must therefore be able to attribute money or assets to the persons on whose behalf they are held."

He added: "This is particularly important for unclaimed sums, since by definition the owner's normal interest in the money is not being exercised."

MP David Davis, the chairman of the Commons Public Accounts Committee which looks at the National Audit Office reports, said the report showed "financial mismanagement" by staff in charge of the fund.

'Serious failure'

He added: "When public bodies hold funds on behalf of citizens they should, at the very least, know whose assets they hold and how much in each case.

"It is a serious failure that the Court Funds Office does not know the ownership of some £10m of assets in their unclaimed balances account.