David Cameron says he has had "relatively regular" meetings and correspondence with Prince Charles, adding: "I think the heir to the throne should have every right to write letters to government ministers or politicians."
Speaking to ITV Wales News, the Prime Minister described the Prince of Wales as a "man with huge passion about public life" and said "I hope he carries on having the strong views that he does".
He also said his government had made the "right" decision in amending the Freedom of Information Act to prevent future correspondence between the monarch and heirs to the throne being published.
From the fate of the Patagonian Toothfish to preserving the memory of some of Britain's greatest explorers, Prince Charles touched upon a great number of varied issues in his now-public letters to Government ministers.
Lawmakers have taken the threat of today's publication seriously enough to amend the law around the Freedom of Information Act so correspondence from the monarch and the heir to the throne cannot be released in future.
ITV News Correspondent Paul Davies reports on the release of the memos - a culmination of a ten-year legal battle.
Prince Charles faces accusations of interference with government affairs after letters made public today showed him raising concerns on a number of issues with ministers, including Tony Blair.
Among the issues raised was an alleged lack of resources for troops on the front line in Iraq, as ITV News Royal Editor Tim Ewart reports.
A summary of the Prince of Wales' correspondence with ministers, which was released today after a ten-year legal battle.Read the full story ›
Prince Charles referenced the freedom of information act in one letter to then-Prime Minister Tony Blair.
The use of the act by Guardian journalist Rob Evans instigated a decade-long legal battle for their eventual release.
In his 2005 letter, Charles wrote: "I much enjoyed the opportunity to talk about a number of issues. You kindly suggested that it would be helpful if I put them in writing - despite the Freedom of Information Act!"
The Prince of Wales urged Tony Blair to support the use of herbal medicines during his time as Prime Minister, further correspondence shows.
In a February 2005 letter, Prince Charles warned that an EU directive on the treatment was having "such a deleterious effect on the complementary medicine sector in this country by effectively outlawing the use of certain herbal extracts".
"I think we both agreed that this was using a sledgehammer to crack a nut," he added.
The legislation, which came into effect in 2011, meant only registered professionals such as doctors could prescribe manufactured herbal remedies.
Despite Charles regularly campaigning for UK regulation to ensure those reliant on herbal medicine were able to get it legally, no such laws have yet been introduced.
The Editor in Chief of Guardian News & Media Alan Rusbridger has said he is pleased letters written by Prince Charles to Government ministers have been made public so that the public can "draw their own conclusions."
We fought this case because we believed - and the most senior judges in the country agreed - that the royal family should operate to the same degrees of transparency as anyone else trying to make their influence felt in public life.
The Attorney General, in trying to block the letters, said their contents could 'seriously damage' perceptions of the prince's political neutrality.
Whatever the rights and wrongs of that assessment, it is shocking that the Government wasted hundreds of thousands of pounds of public money trying to prevent their publication.
Now, after 10 years, we are pleased to be able to share the contents of his correspondence and let people draw their own conclusions.
Clarence House statement in full on the publication of letters written by the Prince of Wales to government ministers.Read the full story ›
Prince Charles told then-prime minister Tony Blair that British armed forces lacked the "necessary resources" to do their job, a 2004 letter shows.
In the correspondence, released after a 10-year legal battle by the Guardian, the Prince of Wales told Tony Blair of his concerns about the performance of Lynx aircraft in high temperatures.
"Despite this, the procurement of a new aircraft to replace the Lynx is subject to further delays and uncertainty due to the significant pressure on the Defence Budget."
I fear that this is just one more example of where our Armed Forces are being asked to do an an extremely challenging job (particularly in Iraq), without the necessary resources.
The letter also included requests to do more to support British agriculture, and expresses pleasure that Blair will be coming to Clarence House for a dinner.
In a response, Blair outlined a number of measures the government was taking to support farmers, and added: "While the Ministry of Defence clearly has to operate within finite resources, our planned investment in future helicopters will be substantial."
The publication of private letters between the Prince of Wales and ministers "can only inhibit his ability to express the concerns and suggestions which have been put to him in the course of his travels and meetings", Clarence House has said in a statement as some of the letters were made public following a lengthy legal battle.