Exclusive: Sources close to heir say he will break with Queen’s habit of discretion by continuing to speak out on issues that matter to him • The long read: what kind of king will Charles III be?

Prince Charles is ready to reshape the monarch’s role when he becomes king and make “heartfelt interventions” in national life in contrast to the Queen’s taciturn discretion on public affairs, his allies have said.

In signs of an emerging strategy that could risk carrying over the controversy about his alleged meddling in politics into his kingship, sources close to the heir say he is set to continue to express concerns and ask questions about issues that matter to him, such as the future of farming and the environment, partly because he believes he has a duty to relay public opinion to those in power.

“He will be true to his beliefs and contributions,” said a well-placed source who has known him for many years. “Rather than a complete reinvention to become a monarch in the mould of his mother, the strategy will be to try and continue with his heartfelt interventions, albeit checking each for tone and content to ensure it does not damage the monarchy. Speeches will have to pass the following test: would it seem odd because the Queen wouldn’t have said it or would it seem dangerous?”

In the past Charles has stirred controversy by lobbying politicians over issues such as genetic modification of crops, education and health. The government has already conceded that if the currently secret “black spider memos” he has written to ministers are ever made public, and readers concluded Prince Charles was disagreeing with government policy, that could “seriously damage” his future role as king.

“The prince understands the need to be careful about how he expresses concerns or asks questions, but I do think he will keep doing exactly that,” said Patrick Holden, an organic farmer, friend of the prince and adviser to him on sustainability. “He is part of an evolving monarchy that is changing all the time. He feels these issues are too serious to ignore.”

The comments came as part of a wide-ranging Guardian investigation into the possible shape of a King Charles III monarchy. Next week the supreme court will consider whether 27 letters between Charles and government ministers should be published following a nine-year freedom of information battle between the Guardian and Whitehall. The government and the palace argue correspondence and meetings with ministers are a necessary part of his preparation for kingship and in 2012, the then attorney general Dominic Grieve said they had to be kept confidential to protect Charles’s position of political neutrality.

Constitutional experts have frequently praised the Queen for almost completely keeping out of public debates on political matters and Charles is said to understand that his ability to speak on matters which have a political element to them will be in a different category to the freedom he enjoys in his current role. Courtiers also argue that his 40 years as heir carrying out thousands of engagements across the country and abroad mean he is uniquely well-placed to relay public opinion.

Facebook Twitter Pinterest The Prince of Wales with the Queen, who has been praised for keeping out of public debates. Photograph: Dominic Lipinski/PA

“Speculation about the Prince of Wales’s future role as king has been around for decades but it is not something we have commented on and nor will we do so now,” said a Clarence House spokeswoman. “The Prince of Wales cares deeply about this country and has devoted most of his working life to helping individuals and organisations to make a difference for the better – and not for his personal gain. He takes an active interest in the issues and challenges facing the UK and around the world through his own work and that of his charities.

“Over the past 40 years in his role as heir to the throne, the Prince of Wales has visited countless places and met numerous people from every walk of life. He carries out over 600 engagements a year. This gives him a unique perspective which has often led to him identifying issues before others which might otherwise be overlooked. He is often described as being ahead of his time and the evidence for this has been well documented and includes leading the work on corporate social responsibility, from as early as the 1980s, demonstrating the benefits of organic farming, as well as finding ways to help young people who are not in employment, education or training through his Prince’s Trust.”

Paul Flynn, a Labour member of the Commons political and constitutional reform select committee, said continued interventions would not be compatible “with the serious job of the monarch to act as someone above politics and above controversy”.

“We know Prince Charles has deep-seated, passionate views, some of which are sensible, some eccentric and some barmy,” he said. “If he continues to be a controversial figure on issues like complementary medicine and country sports he could precipitate a constitutional crisis if he comes up against a government which is bent on some course of action and he disagrees and refuses to sign the act of parliament.”

Flynn said the Queen’s silence on controversial issues had secured the monarchy and made it acceptable in a democracy. He said that if Prince Charles decided to go outside those boundaries as king “he imperils the monarchy”. But one source said Charles got frustrated that people seemed to think he did not understand that being head of state was a different job.

Michael Meacher, the former environment secretary who Charles lobbied over genetically modified crops, suggested that if King Charles wanted to intervene, an unprecedented new system of transparency about his communications with government would be required.

“I would favour the arrangement whereby if letters are received it is made known either in response to a freedom of information request or without prompting so people will know if the king has taken an interest,” he said. “People will be watching to see if the action taken is in line with what is thought to be his view … People are sceptical and suspicious and they have a right to know if the king has taken an interest.”

The Freedom of Information Act protects the royal family’s correspondence from public exposure, so any FOI request would only work if parliament changed the law.

As king, Charles is likely continue to oversee some of the charity operations he has created. Under the auspices of the Prince’s Charities he built up a network of 21 charities, now reduced to 15, and has used several of them to lobby government ministers and officials over causes that matter to him ranging from complementary medicine to traditional architecture. The number of charities in the network may be reduced further but some will remain.