Claims that the Prince of Wales abuses his position by "secret lobbying" for a number of causes have been dismissed in a 30-page rebuttal by a senior aide.
The prince's role will change when he becomes king
The claims were made in a Channel 4 documentary shown on Monday.
Sir Michael Peat says the prince has the right to share his views with ministers and recognises his role will change once he becomes king.
It would be more damaging to the monarchy if he did not use his position to help with issues, he added.
One contributor, Lord Wedderburn, told Channel 4's Dispatches: "If in fact, nothing changed and he became king, then there would be a most almighty fuss and controversy, and eventually the whole fabric of the constitutional monarchy could be threatened."
But in a lengthy statement, Sir Michael said the claim was "misconceived" and "entirely hypothetical".
Lord Haskins, who led the Rural Recovery Task Force following the foot-and-mouth outbreak, said many public figures viewed Charles as a "lobbyist".
They think they have to give a "disproportionate" amount of time listening to his point of view and they know he is trying to use his position to influence policy, he said.
Former personal assistant Elaine Day, who lost a claim against unfair dismissal, said the prince wrote letters addressed and signed off by himself to influential people "a great deal".
She worked at Clarence House in 2005 and described the prince's office as "a very influential lobby group".
"And there are no doors that are closed to that lobby group, every door opens," she added.
However Sir Michael said: "It is ...the Prince of Wales's right - as a Privy Councillor - to consult and advise his Privy Council colleagues on a private and confidential basis."
Letter of complaint
He also dismissed suggestions that Charles's public interventions on issues such as architecture or farming could be viewed as political.
He said it would be more damaging to the monarchy if the prince did not use his position to "help with issues which matter to ordinary people but which have not found their way onto political agendas".
But Professor Stephen Haseler, of campaign group Republic, who also took part in the programme, said: "The prince has admitted that he involves himself with public policy debate, which is by definition political.
"Does the prince also feel free to comment on the future of Trident, on Iraq, Lords reform and so on?
"He cannot do so and retain his position as heir to the throne, which is unaccountable and apolitical."
The programme also claims that a professor at Exeter University faced possible dismissal after a letter of complaint from Sir Michael.
Edzard Ernst, professor of complementary medicine, criticised a draft of a report by the Prince's Foundation for Integrated Health to the press.
A subsequent letter to the vice chancellor led to a disciplinary procedure and was an attempt to silence him, he claimed.
But Sir Michael said the letter was not prompted by the prince and he was not even aware it had been written.