LONDON (AFP) - Britain's heir to the throne Prince Charles is sent papers from confidential meetings of Prime Minister David Cameron's inner circle of ministers, the Guardian newspaper reported on Tuesday (Dec 15).

The revelation, which emerged after a three-year campaign, raises fresh questions over the neutrality of Charles, who is known to lobby ministers on issues close to his heart.

A series of "black spider" memos - so-called because of his spindly handwriting - released in May after another legal battle showed him writing to ministers about issues including army equipment and badger culls.

Charles, 67, has for decades received all memoranda from cabinet meetings which can include planned new laws and secret policy documents, the paper reported.

Others who received them include Queen Elizabeth II and government ministers who are in charge of departments.

Campaign group Republic, which wants to see the abolition of the monarchy, called the situation "quite extraordinary and completely unacceptable".

"Charles has no legitimate need to see cabinet papers at all," its CEO Graham Smith said.

"His political and private interests and the high degree of secrecy surrounding his lobbying mean there is a real danger this information can be abused without any possibility of accountability."

Official guidelines on who should receive official secret documents state that access should be on a "need to know" basis.

A spokesman for the Cabinet Office, the official department which deals with the machinery of government, said it was "established practice" for the monarch and future monarch to receive cabinet minutes.

"It's important that the head of state and her heir are properly briefed," he added.

Charles's office, Clarence House, declined to comment.