Files relating to Prince Andrews numerous business trips will not be released until 2065 - meaning he would have to live until the age of 105 to face public scrutiny
The Duke of York's correspondence with Ministers - including details of dealings as a trade ambassador - came to light in response to a Freedom of Information (FOI) request made to the Foreign Office made by royal biographer Andrew Lownie.
Several requests were made by the royal expert seeking further information on numerous business trips - which were usually paid for by the taxpayer - taken by the Prince, now 63.
Under normal rules, records transferred to The National Archives at Kew from government departments are kept secret for 20 years. But special dispensation is awarded to the Royal Family.
Mr Lownie, however, believes there is a 'culture of secrecy' surrounding royal correspondence and called for 'a much more grown-up approach to the release of royal records'.
He told the Telegraph that he hoped with King Charles new reign 'only pertinent FOI exemptions such as national security, relations with another country, information given in confidence' would be applied alongside data protection provisions.
He said: 'We are in the absurd position that Prince Harry can reveal the most intimate details of royal life from months ago for personal commercial gain and Royal households currently brief against each other, yet historians cannot look at files.'
'Many questions remain about his role as trade envoy, a public appointment paid for by the taxpayer, and his associations with figures such as Jeffrey Epstein.
'There is also a strong public interest in knowing, for example, who is paying for his security now he is no longer a working royal.'
While he described himself as a monarchist, who is currently writing a biography on Prince Andrew, he said it does not mean he does 'not believe the Royal family should not be subject to scrutiny'.
Documents relating to Andrew's brother, the Duke of Edinburgh, Prince and Princess Michael of Kent, and Princess Alexandra also have the same time gap - 105 years from their birth - for release.
Comment: The debate whether any of them should be given such a grace period aside, the other royals mentioned at least haven't been implicated with a high profile paedophile and child trafficker; perhaps those known to associate with sinister criminals should be treated differently? Although if that was the case, King Charles would be under serious scrutiny: The Prince and the pedophile: Charles' connections to pedophilia networks
Prince Andrew was the UK's special representative for trade and industry envoy from 2001 and 2011.
Comment: And, back in 2010, his wife, the Duchess of York, was caught on hidden camera attempting to sell access to Andrew and his connections for £500,000. She told the undercover investigator:
'So if you want to meet him in your business, look after me and he'll look after you ... you'll get it back tenfold.'
He was forced to resign a decade into the job after being pictured with sex offender Jeffrey Epstein in Central Park, New York after the billionaire had been released from jail for serving a 18-month sentence over sex offences.
The Duke had also faced scrutiny over his 'very close' friendship with Saif Gaddafi - son Libyan leader Muammar Gaddafi, and Tarek Kaituni, a convicted Libyan gun smuggler.
Mr Lownie told the Mail yesterday: 'Many questions remain about his role as trade envoy, a public appointment paid for by the taxpayer, and his associations with figures such as Jeffrey Epstein.
'The delays in release create a vacuum for speculation and fantasists. Their release would go some way to restoring trust in institutions, not least the monarchy.'
In a copy of the FOI letter, seen by the paper, the Government said in relation to the release: 'Some information is being withheld under Section 37 (Communications with Her Majesty and honours), section 40 (Personal Information) and section 41 Information Provided in Confidence exemptions.'
Comment: See also: Prince Andrew's links to alleged pedophile and rapist fashion tycoon Peter Nygard revealed in new abuse scandal