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.
Secret letters sent by Prince Charles to government ministers in 2004 and 2005 will be published today.
Supreme Court judges ruled that Charles' correspondence with ministers - known as "black spider" memos because of his distinctive handwriting - will be released following a decade-long Guardian campaign.
The 27 letters to ministers in seven government departments will be published with some redactions to protect the personal data of people other than Charles.
Attorney general Dominic Grieve said the correspondence reflects Charles' "most deeply held personal views and beliefs".
The Government has battled to keep the letters out of the public eye but the Court of Appeal declared the veto unlawful last year - a ruling upheld by the Supreme Court judges in March.
David Cameron said at the time that the decision was “deeply disappointing”.
He said: "This is about the principle that senior members of the royal family are able to express their views to government confidentially. I think most people would agree this is fair enough."
The Prince of Wales and the Duchess of Cornwall are to make their first joint official visit to Ireland and Northern Ireland later this month.
The four-day trip is to "recognise the warm friendship and close cooperation that exists between the UK and Ireland".
In Ireland, the royal couple will meet Irish President Michael D Higgins for dinner, and attend the Sligo Races and other cultural engagements on 19 and 20 May.
In Northern Ireland, where they will be between 21 and 22 May, they will visit Belfast, with a stop at Mullaghmore, where the Prince's great-uncle, Lord Mountbatten, was killed in an IRA bombing in August 1979.
The royal family have donated to the DEC appeal to help the victims of the Nepal earthquake.
Both the Queen and Prince of Wales made personal donations to the appeal launched by leading UK aid agencies.
The Queen, and Charles and Camilla, donated undisclosed sums which will be used by the DEC Nepal Earthquake Appeal to support the work of its 13-member organisations.
The royal family have a long association with Gurkha troops who fight for the UK but are drawn from the men of Nepal, with Charles Colonel in Chief of The Royal Gurkha Rifles.
At the start of investiture ceremonies the Queen enters the room attended by two Gurkha orderly officers, a tradition begun by Queen Victoria in 1876.
The Supreme Court have reached an "unconstitutional decision" by allowing letters written by the Prince of Wales to government ministers to be published, Tory MP Jacob Rees-Mogg has said.
The MP for North East Somerset said the ruling would make it very difficult for Prince Charles to do his job.
"It is the job of the Prince of Wales to interest himself in what his majesty's government is doing that's his role, that's his job", he said.