Britain's Prince Charles has branded a Labour peer "a nutter".

Britain's Prince Charles

Britain's Prince Charles

The 66-year-old royal made the comment about Lord Berkeley after he called for certain reforms to be made on the Duchy of Cornwall.

Charles is said to have questioned Lord Berkeley's state of mind after he introduced a private member's bill into the House of Lords which stipulated that the Prince's estate should be paying the same amount of tax as private companies.

According to Catherine Mayer's new unofficial biography 'Charles: Heart of a King', the royal said during a shooting trip with another unidentified peer: "Is this man Berkeley a nutter?"

Lord Berkeley, 75 - who is a former Labour transport spokesman - has since confessed he is worried about the heir apparent's reign and fears ministers will simply bow down to his desires as "they are scared of crossing him."

He told the Daily Telegraph newspaper: "It's definitely true that he said that about me and if he was asked about it again he would probably repeat it.

"People are allowed to have alternative views to the Prince of Wales, and this demonstrates a worry that I have and will continue to have about what he will do when he becomes king.

"You can't have a situation where he is writing these black spider memos to ministers who then do as he says because they are scared of crossing him."

The former engineer added he is not prepared to drop the bill calling for the Duchy of Cornwall to pay more tax.

He also called for a "more transparent monarchy" and the need to reduce the number of those who are considered part of the Royal household.

He said: "I'm not going to give up on this. I want a more transparent monarchy and I want less members of the Royal family. It's not right for Prince Andrew, for example, to be going round the world at our expense."

So far Clarence House has refused to comment on the claims, saying: "We are not going to comment on hearsay and the opinion of others."