Prime Minister Anthony Albanese is seeking advice as to the legality of former prime minister Scott Morrison secretly swearing himself into additional portfolios.

“Nothing about the last government was real, not even the government himself,” Albanese said in Melbourne on Monday morning.

Albanese said Morrison had been running a “shadow government” that was “unbecoming, cynical and just weird … contrary to the Westminster system”.

Morrison secretly swore himself into the health and finance portfolios, according to a new book by journalists Simon Benson and Geoff Chambers called Plagued.

News.com.au has subsequently reported Morrison was also sworn in as second resources minister, with former deputy PM Barnaby Joyce revealing that in December last year Morrison used his powers to shoot down controversial gas projects touted for the NSW coast.

At the time Greg Hunt was health minister and Mathias Cormann was minister for finance. Cormann was unaware of the unusual arrangement.

A spokesman for Governor-General David Hurley confirmed he appointed Morrison to several additional portfolios, though he did not say what they were as “the decision whether to publicise appointments to administer additional portfolios is a matter for the government of the day”.

“The Governor-General, following normal process and acting on the advice of the government of the day, appointed former prime minister Morrison to administer portfolios other than the Department of the Prime Minister and Cabinet. The appointments were made consistently with section 64 of the Constitution,” the statement from Hurley’s office says.

“It is not uncommon for Ministers to be appointed to administer departments other than their portfolio responsibility. These appointments do not require a swearing-in ceremony – the Governor-General signs an administrative instrument on the advice of the prime minister.