The Australian Federal Police on Saturday confirmed it had received a complaint relating to an historic sexual assault, and would now work with relevant state authorities.

The matter was referred to federal police by Labor senator Penny Wong and Greens senator Sarah Hanson-Young, who had received an anonymous letter detailing historic allegations of rape against a senior government member.

Prime Minister Scott Morrison had also reportedly been sent a copy of the same letter.

The alleged incident reportedly occurred in Sydney in 1988, before the accused man had entered politics.

Ms Hanson-Young said Mr Morrison could not simply rely on police to investigate the allegations.

"We can't have a situation where such a horrific allegation of rape is levelled against a senior member of his government and no one does anything," Ms Hanson-Young said on Saturday.

NSW Police received a report about the allegations in February last year. Its subsequent investigation was suspended after the woman who made the report, then 49, was found dead at a home in Adelaide by South Australia Police on June 24.

A formal statement was not provided when the woman initially met with police in Sydney, NSW Police said, and that process was never completed.

Fronting the media in Adelaide on Saturday, Senator Birmingham backed police to investigate the allegations "free of any sense of political interference or direction". He stressed that everyone had a right to natural justice.

Asked if the accused should stand down, Senator Birmingham said: "I think we should back police to do their job."

Senator Birmingham said he had not received a copy of the anonymous letter. But he said that if he had he would have forwarded it to federal police in line with advice on the reporting of criminal allegations issued this week by AFP Commissioner Reece Kershaw.

Senator Wong issued a further statement on Saturday afternoon, confirming reports that she had made been aware of the allegations in 2019.

"I first became aware of the complainant's allegation when I ran into her in Adelaide in November 2019," she said.

"The complainant reminded me we had met once before. The complainant made an allegation that she had been raped many years earlier by a person who is now a senior member of the federal government."

Senator Wong said the woman had indicated that she intended to report the matter to NSW Police, which she had supported her to do.

"I said that making a report to the appropriate authorities was the right thing to do," she said in the statement.

"I facilitated her referral to rape support services and confirmed she was being supported in reporting the matter to NSW Police."

Labor's Senate leader and foreign affairs spokeswoman said the woman's death was a tragedy, and devastating for everyone who knew and loved her. She said the woman, her family and friends, had been in her thoughts throughout.

"I issue this statement in the interests of transparency, and in the hope that appropriate action is taken to examine her allegation, the circumstances of her death and what can and should be done to help keep people safe and save lives in the future," she said.

Senator Wong said she had also forwarded the letter to NSW and South Australia Police. She had previously contacted South Australia Police to offer her assistance with the coronial investigation, according to her statement.

South Australia Police said the woman's death was a matter for the coroner.

SUPPORT SERVICES:

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: