The High Court has agreed to consider whether sealed letters between the Queen and former governor-general Sir John Kerr at the height of Australia's greatest constitutional crisis should be released to the public.

Key points: Jenny Hocking's request to access the letters was rejected because they are considered private correspondence

Jenny Hocking's request to access the letters was rejected because they are considered private correspondence The letters are held under embargo by the National Archives of Australia until 2027

The letters are held under embargo by the National Archives of Australia until 2027 Ms Hocking said the letters would shed light on what the Queen knew before Mr Whitlam was dismissed

Historian and Gough Whitlam biographer Jenny Hocking has been seeking the release of the letters, held by the National Archives of Australia (NAA), since September, 2016.

She claims the Palace letters, as they are known, could shed light on what the Queen knew in the lead-up to the unprecedented dismissal of Mr Whitlam in 1975.

The High Court today granted her leave to appeal against a majority decision of the Federal Court, which found the letters are personal, and not Commonwealth records.

The letters are held under embargo until at least 2027, as they are classified as private correspondence.

However, lawyers for Professor Hocking argued they should instead be classified as Commonwealth records.

Under the current rules, any release of the letters would require the consent of both the Governor-General and the monarch of the day.

Jenny Hocking says the letters should be classified as Commonwealth records. ( AAP: Peter Rae )

Outside court, Professor Hocking said she was "absolutely delighted" and it was "entirely fitting" that the highest court in the country had agreed to hear her case.

"At stake is our knowledge of history, and our knowledge of what was actually taking place between the governor-general and the Queen at the time of the dismissal," she said.

"[It's] really important material, really important letters that are held by our own archives, but we can't see them.

"The Queen can look at them but we can't."

David Fricker, director-general of the NAA, said he did not dispute the historic significance of the letters, but it was his "legal obligation" to oppose their public release.

"I just want to reassure everybody that the National Archives is caring for these documents and looking after them precisely because they are of such historical significance," he said.

"They wouldn't be in the archive if we didn't want them to be publicly available."

Mr Fricker said he had never been pressured by Buckingham Palace or by Mr Whitlam's family in relation to the letters.