The so-called "palace letters" between the Queen and the former governor-general who played a crucial role in Gough Whitlam's dismissal will remain secret in what a historian has called a "national humiliation".
Professor Jenny Hocking on Friday lost her latest legal fight to access the dozens of letters between Buckingham Palace and Sir John Kerr in the months before the unprecedented 1975 dismissal.
Two of three judges in the Federal Court dismissed her appeal against a decision that the "palace letters", held by the National Archives of Australia, were personal communications rather than official Commonwealth records.
Prof Hocking was ordered to pay $30,000 in costs.
In the upheld decision, the same court in March 2018 ruled the letters didn't have to be released as they were the personal property of the governor-general.
Prof Hocking believed the letters would give insight into the then-governor general's thinking and how much the palace knew.
On Friday, she said she was disappointed for all Australians, who should have access to "such important historical documents".
The letters are embargoed until at least 2027, but the Queen holds a final veto over their release.
"It's more than 40 years since the dismissal of the Whitlam government and it's extraordinary that we're still waiting to see absolutely vital information about that dismissal of an elected government," she told reporters outside court.
"It's a national humiliation that those letters remain embargoed by the Queen and yet they're held in our own archive."
She said she'd have to read the appeal judgment before considering "what our possibilities are going forward".
Australian Associated Press