Secret letters between then-governor-general Sir John Kerr and the Queen at the time of the Whitlam Dismissal should be made public because, while the governor-general's "exercise of the [dismissal] power was personal, and most likely lonely", it was still an official act, court documents say.

The court documents, filed by eminent historian Jenny Hocking's legal team, lay out her High Court claim that the letters, held in the National Archive, have been incorrectly classified as "personal records" and should instead be seen as Commonwealth records that are eligible for early publication.

Sir John Kerr and then prime minister Gough Whitlam in the King's Hall, Parliament House, Canberra on July 11 1974. Credit:Fairfax Archives

If the High Court sides with the Federal Court decision that the documents, which comprise letters and telegrams sent between 1974 and 1977, are personal records, then they will remain secret until at least 2027 and require the permission of the Queen's private secretary for publication.

But if they are Commonwealth records, then Professor Hocking, who was then-prime minister Gough Whitlam's biographer and has written extensively about the Dismissal, would be able to apply for their early release, though that could still be declined on other grounds.