Prince Charles nets £1 million pay rise

He earned more than £15 million from the Duchy of Cornwall estate last year - compared with £14 million the previous year.

Senior sources say the estate, set up in 1337 to provide heirs to the throne with an income, has had an "exceptional year".

The figures will be officially released next month when Clarence House publishes its annual review.

However, a senior MP said the windfall is the equivalent of winning the lottery every month - and called for the prince's private income to be investigated by Parliament.

MPs on the Public Accounts Committee have complained that the complexity of the accounts and lack of public scrutiny give the impression that the estates are managed through a system of "creative accountancy".

However, this allegation is strongly denied by the Palace and Clarence House.

Although the prince generates such a large income, taxpayers foot the bill for royal security, maintenance of Clarence House and official trips.

From his private income, Charles pays the expenses of his wife Camilla - the Duchess of Cornwall - and those of Princes William and Harry.

As a Crown body, the Duchy is tax exempt but the prince voluntarily pays income tax on his estate income.

Senior Labour MP Ian Davidson, who sits on the committee, said: "This once again demonstrates the need for there to be closer examination-of all of the Prince of Wales' expenditure.

"Many of us remain concerned that he is able to spend so much money on fripperies while he obtains tax benefits unavailable to the rest of us mere mortals.

"The committee believes we should have full access to the accounts of the Duchy of Cornwall in order to establish where the tax breaks he receives as a property developer are justified.

"The money that he receives is beyond the dreams of all of my constituents.

"This bumper bonus is the equivalent to winning £1 million on the lottery for every month of the year."

The Duchy's assets are understood to have been boosted by the buoyant stock market - its property holdings have risen to more than half a billion pounds.

The 56,000-hectare (138,000-acre) estate, complete with farms and businesses, generated an income of £11 million after costs.

And its portfolio of investments, worth about £100 million, offered returns of about £4 million last year.

Five years ago, this portfolio returned an income of just £352,000.

Charles's total income has more than doubled in the last five years. There have been calls for him to allow his accounts to be cleared by the Auditor-General, Sir John Bourn.

The Clarence House review will also reveal that the prince continues to be the country's major individual charity benefactor - raising millions for his 16 main charities, which include the Prince's Trust.

A spokesman for Charles last night refused to comment until the figures are officially released.