Prince Charles faces the first ever parliamentary inquiry into his finances after it emerged that he has received a 300 per cent pay rise over the last decade.
In what will be the latest embarrassment for the royal family, an analysis of the Duchy of Cornwall's accounts reveals that his income has soared from £3 million in 1993 to almost £12m last year.
The duchy was a gift from the Queen on the prince's 21st birthday. It is now worth more than £460m yet pays none of the normal business taxes. Charles receives all his income from the estate, which owns 144,000 acres of land and runs a commercial enterprise including the sale of organic food products.
Charles saw his salary jump £2m last year after his tenants' rents increased.
Yet despite now being worth more then £460m, the duchy enjoys lucrative tax breaks that exempt it from paying corporation tax and capital gains tax.
Over the last decade it is estimated to have cost the taxpayer more than £20m. In 1999 the Duchy sold thousands of shares to help fund a £50m property deal. He made a large profit on the share sale, yet paid no tax on this. One expert told The Observer he estimates this could have saved Charles some £10m.
Many Labour MPs believe the duchy should pay commercial taxes.
The inquiry will look at the public cost of running the Clarence House office of Charles's partner, Camilla Parker Bowles. The ex-home of the late Queen Mother was refurbished at a cost of £6.5m with funds coming from the taxpayer and duchy income.
MPs are also likely to examine any duchy contracts with a firm run by Michael Fawcett, Charles's former aide who resigned after it was revealed gifts given to Charles were then sold by his staff. Fawcett, who earned the nickname 'the Fence', continues to remain vital to Charles's life organising events and overseeing the renovation of his main properties.
Instead of being paid as a royal employee, Charles finances Fawcett through the former aide's new London firm, Premier Mode Events.
A Clarence House official defended Charles's 300 per cent rise. 'The duchy is required to be run on a commercial basis and the Prince of Wales pays tax on his income like anybody else, and uses the majority of his after-tax income to support his official and charitable work,' she said.