The Prince of Wales says he will stop speaking out on topics he feels strongly about when he becomes king, as he is "not that stupid".
He has campaigned on issues such as the environment for decades, but says he would not do the same as monarch.
Speaking in a BBC documentary to mark his 70th birthday, Prince Charles said that he would continue making interventions was "nonsense".
He said he would have to operate within "constitutional parameters".
He has campaigned on issues including the environment, wildlife preservation, architecture and the use of GM crops.
In the hour-long program, he was asked about what some people had called his "meddling", but he had always tried to remain "political non-party".
He said: "I think it's vital to remember there is one room for one sovereign at a time, not two.
"So, you can't be the same as the sovereign if you're the Prince of Wales or the heir.
"But the idea, somehow, that I'm going to go on in exactly the same way, if I have to succeed, it's complete non-sense because the two – the two situations – are completely different."
Asked whether his public campaigning would continue, he said: "No, it won't. I'm not that stupid.
"I do not understand that it is separate exercise. So I understand entirely how that should operate."
Documentary film maker John Bridcut, who was followed by the royal for 12 months, said Prince Charles "bridled a bit" at the use of words, and instead preferred to think of his interventions as "motivating".
The heir to the throne said: "If it's meddling to worry about the inner cities as I was in 40 years ago, then if that's meddling I'm proud of it."
By Nicholas Witchell, royal correspondent
He has spent his adult life trying, as he puts it, "to make a difference". The Prince of Wales often says about topics about which he feels deeply: the environment, GM crops, inner cities, architecture, education, homeopathic medicine and others.
Prince Charles has been accused of "meddling". It has, on occasion, caused irritation in the government departments that have had to respond to his heart "black spider" handwritten letters raising, which is often but often, some issue which has come to the prince's attention.
It has all given rise to a greater concern. Does Prince Charles fully appreciate that, when will he and Britain's king, these interventions will have to stop?
Those who know him have said that he does understand that there is a line which, as sovereign, he can not cross.
They've said that he fully understands that, as king, he would have to stop "campaigning".
Prince Charles himself has always failed at saying as much publicly. He said to feel that any reference to how he would function as monarch could be seen as being respected to his mother.
However, with the Queen now in her 93rd year, and with Prince Charles about to celebrate his 70th birthday, he has finally said – publicly and explicitly – that will have to stop as soon as he becomes king.
"You operate," he says in the BBC documentary, "within the constitutional parameters".
It is reasonable to say that his assumptions will be heard with some relief within whitehall and the corridors of power.
Mr. Bridcut said: "People who think he's hanging around, longing to be king, are very mistaken.
"It's not something he's dying to assume because inevitably it will only arise after the death of his mother."
"The Duchess of Cornwall, who is also interviewed in the documentary," makes the point that this burden does not weigh heavily on its shoulders.
The BBC has been given exclusive access to the film Prince Charles, who turns 70 on November 14.
Also appearing on the program, the Duke of Cambridge said he would like to spend more time with his grandfather – Prince George, Princess Charlotte and Prince Louis.
Prince William said, "when he's there, he's brilliant" but "we need him there as much as possible".
'People on his side'
By Roger Harrabin, BBC environment analyst
The prince was warned decades ago about human-induced climate change. It was controversial to be at some time, but now there is a scientific consensus on the threat.
On wildlife he right predicted a huge loss of species. He campaigned against rainforest destruction, and he will be pleased at the recent focus on the impact of forests, and therefore on the climate.
His concern for soil sounding to some observers, but now acknowledges that many areas of crisis and soil degradation and loss.
On these matters, the mainstream has flowed towards the future monarch.
On GM crops, the Prince remains in conflict with the scientific establishment.
On other hobbies, such as homeopathy and architecture, he has rather than fact expressed opinion – but still he'll have some people on his side.
- Prince, Son And Heir: Charles At 70, will be screened on BBC One on Thursday November 8 at 9pm.