The MPs on the House of Commons Public Accounts Committee have demanded Prince Charles open his confidential accounts to full scrutiny amid claims of tax avoidance running into millions of pounds.
They have written to the heir to the throne telling him they want the National Audit Office to be able to inspect the finances of the Duchy of Cornwall, his main source of income.
PAC chairman and former Tory Minister Edward Leigh said he wants to know how much the Duchy of Cornwall and the Duchy of Lancaster, which provides the Queen with an extra income, are exempt from corporation and capital gains tax.
One expert has calculated the move could save Prince Charles an annual £500,000.
Leigh and his fellow PAC members have written to Prince Charles claiming that it is wrong that he has escaped paying millions of pounds over the years.
But royal officials strongly deny any financial impropriety, and point out that he has made public his tax affairs and voluntarily pays income tax.
But this has not satisfied the MPs on the PAC who have challenged both the prince and chancellor Gordon Brown to make the full details of the prince's Duchy of Cornwall account public.
The Treasury has previously backed Prince Charles and the Queen over keeping the Duchies' accounts confidential and free of corporation and capital gains tax saying they are for the 'sole purpose' of providing an income for the sovereign and her heir, and provided an element of independence for them from the government of the day.
The Duchy says there is no need for the NAO to audit them as they are already fully scrutinised by PricewaterhouseCoopers.
