It is somewhat ironic that this question has arisen over the management of the Duchy of Cornwall, the Prince's primary source of income. This estate was created by Edward III in 1337 with the specific aim of securing financial independence for his son. It has certainly provided a handsome income for royal heirs ever since. The Duchy incorporates 56,000 hectares of prime residential, commercial and agricultural land, spread across several English counties. The whole estate is now estimated to be worth £463m.

Prince Charles does not have access to the estate's capital. But he draws the revenue, worth some £13.3m a year. This is used to pay for both his public and private expenditure. The main danger identified with this arrangement by the Public Accounts Committee is that Prince Charles has begun to exert an influence on how much revenue the estate yields. He personally hires those responsible for managing the Duchy. This is in stark contrast to the Queen, who has no aspirations whatsoever regarding the management of her own estate, the Duchy of Lancaster. In the view of the Public Accounts Committee, Prince Charles should be more like his mother.

Yet there is nothing inherently wrong with the Prince taking an interest in the running of his estate. It is arguably his prerogative. And Duchy Originals - the Prince's organic food range - has become a commercial success, in part due to his efforts. This is laudable. But if the Prince is going to actively attempt to maximise the revenue from his estate - or dabble in the highly competitive food industry - he should not be given preferential tax breaks by the Treasury. At present, Prince Charles's estate is exempt from corporation tax and capital gains tax. This must end forthwith.

Also unsustainable is the degree to which the Prince's accountants feel justified in concealing their master's finances from public scrutiny. The Public Accounts Committee is right to call for the National Audit Office to examine the Prince's books in future. The Royal finances should be subject to the same disclosure requirements as any other accounts presented to Parliament. This is as true for those such as the Queen and Prince Charles, who live off their estates, as for those Royals who are supported by the Civil List. The Royal Family must accept that it performs a public function and that its finances are firmly in the public interest.