The book Plagued, written by journalists Simon Benson and Geoff Chambers, contains highly detailed information about how Morrison as prime minister dealt with the COVID-19 pandemic and a number of security challenges including China, nuclear submarines and the Russian invasion of Ukraine.

Labor senator Tony Sheldon asked officials from the Department of Prime Minister and Cabinet on Friday what steps were being taken to deal with what appeared to be cabinet leaks.

The deliberations of cabinet and its various committees are ordinarily considered confidential.

Acting deputy secretary John Reid said his department was not aware at the time that Mr Morrison had been briefing reporters about cabinet matters.

Reid said the department had reviewed the book and concluded it appeared to contain disclosures from cabinet and cabinet committees.

“Our conclusions were that it certainly appears to reveal information that is, or was until revealed, cabinet material and would ordinarily be protected under the principle of cabinet confidentiality,” he said.

Asked whether disclosures about discussions on national security matters such as nuclear submarines and Russia’s invasion of Ukraine could harm Australia’s interests, Reid said: “It may, senator.”

Reid said there was a long-standing convention on the confidentiality of cabinet and cabinet deliberations.

“(But) of course the prime minister of the day always reserves the prerogative to disclose or release information from cabinet meetings,” Mr Reid told the Senate estimates hearing.

He said it had been referred to the attorney-general’s department because that agency was responsible for any possible criminal action relating to disclosures.

Senator Sheldon said it was a matter of “great concern”.

“It’s more than appropriate it’s been sent to the attorney-general’s department,” he said.

Asked whether the department had reviewed the book on the basis of a reference from Prime Minister Anthony Albanese’s office, Mr Reid said: “It was on the basis of news media purporting to suggest there was cabinet material in the book. It seemed appropriate we should have a look at it.”

It is highly unlikely action would be taken against either of the journalists, but Mr Morrison could receive a “please explain” letter.

Morrison is also the subject of an inquiry by former High Court judge Virginia Bell after it was revealed he had secretly appointed himself to five ministries.

The solicitor-general found Mr Morrison did not break any laws in secretly taking on the portfolios between 2020 and 2021, but that it went against the principles of “responsible government”.

The Bell report will be handed down on November 25.

House of Representatives Speaker Milton Dick rejected a request to refer Mr Morrison to the parliamentary privileges committee, advising there wasn’t enough evidence to establish he had knowingly and deliberately misled parliament.

Former prime minister Tony Abbott has described Mr Morrison’s conduct as “highly unconventional, highly unorthodox and shouldn’t have happened”.