Australian Prime Minister Scott Morrison on Monday stood by an unidentified Cabinet minister against calls for him to step down over an allegation that he raped a 16-year-old girl more than 30 years ago.

The accusation has created a cloud over the 16 men in Morrison’s 22-minister Cabinet and is feeding complaints of a culture within Parliament that is toxic for women.

The allegation was contained in an anonymous letter sent to the prime minister’s office and to three female lawmakers last week.

The letter contained a statement from a complainant that detailed her allegation of a rape she said occurred in New South Wales state in 1988.

The woman, who has not been publicly identified, reported the allegation to police before taking her own life in June at age 49.

Morrison said the Cabinet minister “vigorously and completely denied the allegations.”

Morrison said he forwarded the letter to police and discussed the allegation with the federal police commissioner. Morrison said he did not intend to take any further action.

“We can’t have a situation where the mere making of an allegation and that being publicised through the media is grounds for … governments to stand people down simply on the basis of that,” Morrison said.

The Ministerial Code of Conduct states a “minister should stand aside if that minister becomes the subject of an official investigation of alleged illegal or improper conduct.”

Some within the government argue that because the complainant is dead, her allegation is no longer under official police investigation because a conviction is unlikely.

Sen. Sarah Hanson-Young, a minor Greens party lawmaker who received the anonymous letter, said the minister must step down pending an independent investigation by a former judge.

“It is just not right to suggest that this type of allegation could linger, hang over the heads of the entire Cabinet,” Hanson-Young said. She said the accusation erodes the belief that the government takes sexual assault seriously.

Marque Lawyers managing partner Michael Bradley, who represented the complainant when she took her accusation to police, said the allegation cannot be resolved through the criminal justice system because she has died. The minister should step down while some independent inquiry investigates the evidence, Bradley said.

“His position is pretty clearly untenable and he should step aside or be stood aside until this matter can be addressed and resolved,”

Bradley said.

The disclosure comes two weeks after Morrison apologised in Parliament to a former government staffer who alleged she was raped by a more senior colleague in a minister’s office two years ago.

Brittany Higgins quit her job in January and reactivated her complaint to police after initially not pursuing the case because she felt it would have affected her employment.

The colleague, who has not been named publicly, was fired for breaching security by taking Higgins into a minister’s office following a night of heavy drinking.

Three other women have made sexual misconduct allegations against the same man since Higgins went public with her complaint. A government staffer who alleged she was raped by the man last year told The Weekend Australian newspaper the attack wouldn’t have happened if the government had supported Higgins’ initial complaint.

Morrison responded to Higgins’ public complaints by appointing government lawmaker Celia Hammond to work with political parties to investigate Parliament House culture, improve workplace standards and protect staff.