Scott Morrison is watching a scandal over his secret cabinet self-appointments unfold from the safety of the back benches.

But contamination from his radioactive prime ministership is spreading through Australia’s system of government and now, at the very top, threatens Governor-General David Hurley, who signed off on five duplicate Morrison ministries.

A new call for a Royal Commission into the GG’s role hints at looming trouble for an office which must be seen to float above politics.

UNSW Law Professor Rosalind Dixon says Mr Morrison proposed to change cabinet so radically by giving himself secret powers overlapping with his colleagues’ that the GG should have asked if it threatened the constitutional principles his job exists to uphold. It is not clear he ever did.

“We need to hear from him,” she said.

“Either we need transparency or a clear recognition on the part of both the Prime Minister and the Governor-General that relevant appointments were made in error – or we need a Royal Commission.

“I think, unfortunately, this is actually now in that (Royal Commission) category.

“It might well be unconstitutional to give an overlapping portfolio.

“He has to explain himself. Unless and until he does satisfactorily, I don’t think he has discharged his responsibilities.”

A single minister usually has power over a portfolio. Secretly dividing it could lead to conflicting decisions or legal challenges; Professor Dixon says the GG should have sought assurances about such problems before approving the appointments.

Royal Commission powers to compel witnesses might pierce the secrecy that shrouds most all vice regal conversations. Those in the know say confidentiality is the default presumption for all tricky discussions at Government House because it allows public service advisors to speak frankly – which, naturally, leads to good decisions.

Checks and balances questioned

PM Anthony Albanese will release a solicitor-general’s review of Mr Morrison’s appointments on Tuesday. It is expected to find there were no strict illegalities but that his predecessor violated principles of responsible cabinet government.

Anthony Albanese will release an inquiry into Scott Morrison’s appointments on Tuesday. Photo: AAP

On Monday the PM was urged to make sure that an expected followup public inquiry extends to the people who had been around Morrison.

Unusually, the GG’s office spoke out too, saying laws should change so ministerial appointments are always made public, which would have soon stopped Mr Morrison.

Vice regal contributions to the 24-hour news cycle are most unusual. But they are less so than the prospect of the GG, whose office is, legally, one of Parliament’s three component parts, testifying before one of its committees.

For Mr Hurley this might be the paradox that hangs over his final couple of years in high office: needing to remain bigger than politics while facing questions about a hot political scandal.

Liberal MP Bridget Archer said Australians need an explanation for why democratic checks and balances did not stop Mr Morrison, including the GG’s role.

Whether any inquiry would ever be so specific and what powers it has is a matter for Mr Albanese (or, more accurately, cabinet).

Historian Jenny Hocking won a landmark High Court case against the royal right of secrecy when she forced the release of letters between previous governors-general and Buckingham Palace that revealed the latter’s deep involvement in the 1975 dismissal four decades after the fact.

The Queen’s correspondence with John Kerr revealed the Palace’s involvement in the 1975 dismissal. Photo: Getty

A governor-general who objects to a PM’s plan can only push back so far, Professor Hocking notes, but she says the reported absence of any references to Mr Morrison’s self-appointments from the GG’s seemingly otherwise detailed diaries points to the bigger problem.

“A diary is a decision for the Governor-General’s staff and the Governor-General himself,” she said. “That is not an issue for the PM to advise a Governor-General.

“But … if Scott Morrison advised the Governor-General against making it public, then we deserve to know that.

“The secrecy is really, immensely problematic and we’re very badly served by it.

“The only thing that will get to what’s actually going on is a Royal Commission. Only then can we then know what needs to be done to fix this.

“History becomes rewritten once secrecy is stripped away.”

Public in the dark

Greens Senator David Shoebridge says a pattern is emerging in which the Governor General’s Office seems to often keep details from the public. This he says, makes a public inquiry awkward and necessary.

“The convention in Australian politics is that the Governor-General is above political scrutiny, but when so many other conventions have been shown the door under his stewardship, it’s hard to see how that one can seriously hold,” Senator Shoebridge said.

Government House says things are as they have always been.

And the top advisor to two previous governors-general told The New Daily these decisions were Scott Morrison’s and nothing that can change that.

“The Governor-General is duty-bound to accept the formal advice of his or her ministers, and Governor-General Hurley did just that,” Malcolm Hazell, a former Official Secretary to the head of state said. “He is entitled to expect that advice tended to him is constitutionally and legally proper.

“Ministers usually ensure with the assistance from their departments, that advice has been thoroughly framed and contested.

“It can hardly be the responsibility of the Governor-General to explain, defend or prosecute that advice.”

A spokesman for the Office of the Official Secretary to the Governor-General flatly denied any change to accepted practice in making the GG’s decisions public:

“There is no secret or conspiracy in the office’s reporting.

“The office routinely publishes details of swearing-in ceremonies and gazettes the details of when the Governor-General has directed a Minister to hold office.”