Helen Haines has branded Scott Morrison's move to secretly install himself in at least three ministries as extraordinary and alarming, calling for the former prime minister to explain himself.
The Independent member for Indi has welcomed an investigation into the legality of the appointments by the Department of Prime Minister and Cabinet.
"It is a most extraordinary and alarming set of circumstances. There is so much we don't know. We deserve an explanation around this. Is this setting some kind of strange precedent?" she told the ABC.
Ms Haines says while there was uncertainty around the pandemic and what would happen if the health minister fell ill, there was no reason for the secrecy.
"There is no question that during this period we were in a most difficult time," she said.
"One could understand how the prime minister may have wished to ensure that there was a safety net, particularly around the role of the health minister.
"But the fact he chose not to tell anyone about this, the fact many members of his cabinet didn't know about this, but this covered multiple portfolios.
"The prime minister has a responsibility to inform the parliament, the public and to inform his cabinet."
Anthony Albanese has received legal advice on whether his predecessor breached the constitution.
He was briefed by his department on the constitutionality of Mr Morrison's actions while in government, after returning to Canberra on Monday afternoon.
On the weekend, The Australian reported Mr Morrison swore himself in as health minister and finance minister, alongside his own ministers, after the start of the COVID-19 pandemic in March 2020.
He also swore himself in as resources minister in 2021 and used his powers to overturn a decision by former minister Keith Pitt to approve a controversial gas project off the NSW coast, according to news.com.au.
On Monday evening, Mr Pitt issued a statement saying he was unaware Mr Morrison had joint oversight of his portfolio and that he stood by the decisions he made.
"I stand by the decisions I made as a minister, the fact that they were discharged correctly and they met all of the requirements under the ministerial standards," he said.
Former Liberal prime minister Malcolm Turnbull said the revelations about the man who toppled him from the leadership were appalling and against the traditions of Westminster parliamentary democracy.
"I'm astonished Mr Morrison thought he could do it, astonished that prime minister and cabinet went along with it," he told ABC television's 730 program.
"I'm even more astonished the governor-general was party it to. This is sinister stuff."
A spokesperson for Governor-General David Hurley says he followed processes consistent with the constitution when he appointed Mr Morrison to the additional portfolios.
"It is not uncommon for ministers to be appointed to administer departments other than their portfolio responsibility," the spokesperson said in a statement.
"These appointments do not require a swearing-in ceremony. The governor-general signs an administrative instrument on the advice of the prime minister."
Opposition Leader Peter Dutton said he didn't know Mr Morrison had sworn himself into the cabinet positions.
"Obviously the prime minister had his reasons, his logic for it, but it was not was not a decision that I was a party to or was aware of," he told ABC Radio on Monday.
Mr Dutton also said he didn't know whether Mr Morrison had sworn himself in as defence minister, which was his former cabinet position in the coalition government.
© AAP 2022