SYDNEY • Australian police are looking into an alleged rape that occurred decades ago and is said to have involved a minister now in Prime Minister Scott Morrison's government.

Federal police said in a statement yesterday that they received a complaint in relation to a sexual assault and will be liaising with the state authorities, without providing further details on the alleged assailant.

The alleged incident took place in 1988, ABC's Four Corners news programme reported, citing an anonymous letter shared by a source close to the victim.

Two senators said they received a copy of the complaint which involved a senior member of the federal government, adding that it was also sent to the Prime Minister.

Opposition Labor Party Senate leader Penny Wong said it was a rape that took place "many years earlier", while Greens Senator Sarah Hanson-Young called the allegation "disturbing" and of a "criminal nature".

The revelation comes less than two weeks after Mr Morrison ordered a probe into workplace culture at Parliament House, after a former government media adviser said she had been raped in the building by a fellow staffer in 2019.

When asked whether the minister involved should stand aside, Finance Minister Simon Birmingham said yesterday that processes needed to be followed.

"Everybody is entitled to natural justice, and it's important to back the police to do their job," he told reporters in Adelaide.

"We have to go back to the appropriate authorities, the police, (for them) to do everything they can to investigate and to their satisfaction, determine the appropriate course forward, free of any sense of political interference or direction."

Ms Wong said her office had received the anonymous letter, which included what appeared to be a statement prepared by the complainant relating to the alleged rape.

The woman who made the allegation died in June last year, Ms Wong added, pointing out that she first became aware of the complaint when she ran into the alleged victim in Adelaide in November 2019.

The latter said "she had been raped many years earlier by a person who is now a senior member of the federal government".

The woman said she intended to report the matter to New South Wales police, according to Ms Wong.

BLOOMBERG