The escrow account holding the €14.3bn in unpaid taxes and interest that the European Commission ordered Apple to pay to the Irish state lost €249m of its value last year.

This means the funds in the account stood at €14.02bn at the end of last year, according to a report by the Comptroller and Auditor General (C&AG) .

The C&AG's Report on the Accounts of the Public Service 2019 says a "third country adjustment" reduced the balance by €209m while there were also tax charges of €3m.

The third country adjustment reflected the payment of tax due to another country from Apple.

The report does not state which country was involved.

"The remaining €37 million decline for the year reflects the current negative interest rate environment and negative yields on highly-rated euro sovereign and quasi-sovereign bonds, and fund operating expenses," it says.

Last year the C&AG warned that the escrow account could lose €70m of its value in 2019 due to poor interest rates on international markets.

Between May of 2018 when the money was transferred into the account and December of that year the decline in value of the fund was €16 million.

The C&AG report also states that just over €4m in costs were also incurred by other state bodies as part of the State aid recovery process and the establishment of the escrow fund.

"This includes all legal costs, consultancy fees and any other associated costs," the report says.

"It excludes the costs of the appeal case taken to the European Courts."

In August 2016, the Commission issued a decision that concluded that Ireland had given illegal State aid to Apple.

That was overturned by the General Court of the European Union in July of this year, and last week the European Commission said it would appeal the decision to the Court of Justice of the European Union.