Scott Morrison’s former cabinet members are unloading on his decision to secretly appoint himself to multiple portfolios ahead of a report into the matter being handed down.

Former Coalition treasurer Josh Frydenberg said he felt “angry, hurt, confused, dumbstruck” after finding out via social media the former PM secretly swore himself into his portfolio.

Mr Frydenberg told author and Nine newspapers columnist Niki Savva his former leader still hadn’t apologised for his actions.

“I don’t think there was any reason for Scott to take on the additional Treasury portfolio,” he told Ms Savva, according to an extract from her upcoming book on the Morrison regime published on Friday.

Mr Morrison appointed himself minister of the departments of health, finance, industry, science, energy and resources, treasury and home affairs, without the knowledge of the appointed ministers.

Mr Frydenberg called Mr Morrison’s actions “extreme overreach”.

Former finance minister Simon Birmingham labelled it the same, saying there was no need for Mr Morrison to take on portfolios beyond health and possibly finance.

“People can understand the initial decisions as it relates to health and even possibly finance taken at the absolute height of concern around the COVID pandemic,” he said in Canberra.

“The latter decisions were a form of overreach and there’s not necessarily a clear explanation.”

Senator Birmingham said the opposition would support any changes to the law to ensure such actions don’t happen again.

“What matters now is how action is taken in the future to ensure transparency about any such decisions,” he said.

“We will give full support to any legislation to ensure transparency in the future.”

Former High Court judge Virginia Bell was asked by Labor Prime Minister Anthony Albanese to inquire into the portfolios issue after the solicitor-general found Mr Morrison’s action had “fundamentally undermined” the principles of responsible government.

Mr Albanese asked for the inquiry to explore how and why the action was taken and who knew about it.

Ms Bell’s report will be made public later on Friday.

The solicitor-general found it was “impossible for the parliament to hold ministers to account for the administration of departments if it does not know which ministers are responsible for which departments”.

Ms Bell was also asked to look at the implications arising from the appointments for the functioning of departments and for accountability and public confidence in government.

She will make recommendations to the government on any changes which could provide greater transparency and accountability.

The government has pledged to start work on implementing any recommendations as early as next week.

Deputy Liberal leader Sussan Ley dismissed reports the Coalition had determined to downplay the severity of Mr Morrison’s actions and said it would support closing the loophole that was exploited.

She did not comment on reports the former prime minister refused to be interviewed for the inquiry.

Former Liberal prime ministers John Howard, Tony Abbott and Malcolm Turnbull have all expressed concerns about Mr Morrison’s action.

The health and finance portfolio roles began in March 2020, while he started as industry minister in April 2021, and home affairs and treasury in May 2021.

He justified the action by saying the only time he used his extra powers was in vetoing the PEP11 resource exploration project off the NSW coast.

Mr Morrison intended the powers to be used only in extreme circumstances “due to incapacity or in the national interest”.

They had not been made public because there was no consistent process for publication, he said, but in any case, the authorities were legally valid.

“I can only state that I took the decisions I did as prime minister with the best of intentions to do all I could to protect Australia in the face of multiple crises,” he said in a statement in August.

-AAP