The outburst comes as the Prince of Wales revealed in a new documentary he will stop speaking out on issues he cares deeply about once he becomes king.
But anti-royal campaigners Republic said he has already said too much as heir to the throne and his attempts to influence Government policy have gone beyond what she should be expected.
Republic said: “The royal PR machine is facing a crisis as Charles prepares to take the throne.
“Charles has routinely abused his position of power, privately lobbying Cabinet ministers and influencing Government policy with his own political agenda.
“It’s unsurprising that royals are rushing to change Charles’ public image as he prepares to become king, but does he really expect us to believe he won’t capitalise on all the powers he’s about to inherit?
“King Charles is just around the corner and we should be having a wide-ranging national debate about our country’s future, not a coronation by default.”
The Prince has been vocal in efforts to help protect the environment as well as protection of endangered species and GM crops.
Prince Charles has faced accusations of meddling for much of his life as Britain’s longest ever serving heir to the throne.
However a former cabinet minister said he doesn’t expect monarchs not to have views.
Lord Hain, who served as Secretary of State for Wales, Northern Ireland and for Work and Pensions in Tony Blair and Gordon Brown’s cabinets, said he often spoke with Prince Charles and “welcomed” those discussions.
He said: “I’ve never been a monarchist, but if you believe in a monarchy, then I don’t see why the monarch currently or the future monarch should be expected to be completely view-less and silent on everything.”
Asked if he thought it was a shame that Charles has said he will not speak out on issues, Lord Hain said: “No. I respect his point of view, just as I respected our dialogues when I was in government.
“When I was a Cabinet minister I had regular interactions with the Prince of Wales and I welcomed those.
“Mostly we agreed. And he made very valuable and interesting suggestions on housing, on the environment, on the necessity for complementary medicine to run alongside and be interchangeable with conventional medicine under the National Health Service.
“We agreed on all of those things, particularly the latter, where we were in a minority.
“We disagreed on hunting with hounds, but that’s fine.
“So I’ve never had a problem with that. And I think the British public … I think there’s a different relationship with the monarchy now.
“I don’t think we expect the monarchy to be either stony-face silent or to have no views.
“I’ve always found the Queen extremely well-informed whenever I was discussing, for example, Northern Ireland with her, or Wales in my capacity as a Secretary of State.”
In an hour-long documentary to celebrate the Prince’s 70th birthday which will be aired on BBC One tonight, he confirmed he would stop making the same interventions he has in the past.
Prince Charles said: “If it’s meddling to worry about the inner cities as I did 40 years ago, then if that’s meddling I’m proud of it.
“I think it’s vital to remember there’s only 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, is complete nonsense because the two – the two situations – are completely different.”
Asked if he would continue his campaigning, the Prince said: “No, it won’t. I’m not that stupid.
“I do realise that it is a separate exercise being sovereign. So of course I understand entirely how that should operate.”
Prince, Son And Heir: Charles At 70, airs on BBC One on Thursday, November 8 at 9pm.