Campaign group Republic, which got the information after a three-year battle, called the prince`s access "wrong".
The Cabinet Office said the Queen and her heir should be "properly briefed". The precedent book was written in 1992, showing the arrangement has been in place for more than 20 years.
The book says the need for secrecy with the documents is so great that "special care in circulation and handling" is required, and cabinet ministers are handed their copies in person.
"The standard circulation for cabinet memoranda includes the Queen, the Prince of Wales, all members of the cabinet, any other ministers in charge of departments, the attorney general and the chief whip," it says.
"A few other senior ministers may receive copies at the prime minister`s discretion... Ministers of state and junior ministers do not normally receive memoranda."
`No legitimate need`
Four chapters were released to Republic after the Cabinet Office failed in its bid to avoid making it public.
Republic has written to Prime Minister David Cameron, calling on him to end the practice of sharing the documents with the prince.
"It is plainly wrong that Charles can lobby on new policy proposals even before the public are aware of the existence of such proposals," the letter says.
Republic`s chief executive Graham Smith said the prince had "no legitimate need" to see the papers, and called the practice "quite extraordinary and completely unacceptable".
"Charles is essentially a minister not attending cabinet," he added. Labour MP Paul Flynn, who has called for a parliamentary inquiry, said this made the prince the country`s "best-informed lobbyist".
A Cabinet Office spokesman said: "It has been established practice for many years that the sovereign and the heir to the throne receive the minutes of cabinet meetings.
"It is important that the head of state and her heir are properly briefed." Earlier this year, following another Freedom of Information Act battle, the so-called "black spider letters" sent by the prince to ministers were released.
Sent over a number of years, the letters covered a range of issues including conservation, defence spending, badger culls, the NHS and homeopathy.
More about:
