Three police agencies have been notified of a letter sent to the Australian prime minister, Scott Morrison, making an allegation of rape against a federal cabinet minister relating to his time before entering parliament. The ABC’s Four Corners first reported the letter on Friday night. It included an attachment reportedly from a now-deceased woman alleging she was raped in 1988. The letter urged Morrison to establish an independent investigation into the alleged sexual assault. The opposition Labor leader in the Senate, Penny Wong, and the Greens senator Sarah Hanson-Young also received the letter and told Guardian Australia they forwarded it to police. NSW police on Friday night confirmed the alleged victim contacted them in February 2020, telling detectives from the child abuse and sex crimes squad she had been raped by the man. NSW police set up Strikeforce Wyndarra to investigate. The woman had engaged a lawyer and told friends about the allegation, but took her own life in June 2020, the ABC reported. In a statement, NSW police said “investigators were advised that the body of a 49-year-old woman was located at a home at Adelaide by South Australia police” in June last year. The investigation was then suspended. The woman did not provide a formal statement in February 2020 and NSW police were unable to complete the process before the alleged victim’s death four months later. SA police were “continuing to prepare a report for the coroner,” the NSW police force said. Wong told Guardian Australia on Friday night that her office “received an anonymous letter which was also addressed to the prime minister and senator Hanson-Young”. “The contents of the letter, and an attachment which appears to be a statement prepared by the complainant, relate to an allegation of rape,” Wong said in a statement. “I understand the complainant reported this allegation to the NSW police force and South Australia police. I have forwarded the letter to the NSW police force, South Australia police and the Australian federal police to assist in any investigations which may be under way.” Wong said she hoped appropriate action was taken “to examine the allegation”. Hanson-Young said on Friday night: “This morning I received information regarding a disturbing and a very serious allegation of a criminal nature against a senior member of the government.” The Greens senator said following advice given to the prime minister by the AFP commissioner this week – following Brittany Higgins’ rape allegation – she spoke with the police commissioner on Friday “who is now taking steps in relation to this information”. In the statement attached to the letter, the alleged victim said she had been anally raped by the man when she was 16. “If this story does become public knowledge, I hope that it will encourage other women to come forward,” she wrote. A friend of the woman told Guardian Australia on Friday the alleged rape and her death last year had been “a source of great anguish to the many friends of the young woman concerned”. “All we wanted was justice for her – it seems now we’re inching closer to that in some way.” For two weeks the Morrison government has defended its handling of an allegation by Brittany Higgins – a former Liberal staffer – that she was raped in the ministerial office of Linda Reynolds by another government staffer in March 2019. After Morrison publicly rebuked Reynolds for failing to inform him of the alleged rape, the Australian federal police commissioner, Reece Kershaw, wrote to Morrison and other MPs underlining the need for alleged sexual assaults to be reported swiftly to the AFP. In the letter, sent on Wednesday, Kershaw said MPs and senators, their staff and offices “may receive complaints or allegations of sexual assault from a variety of sources, including victims themselves”. “Such matters should be reported to the AFP without delay, taking into account the rights and privacy of the victim, and irrespective of the jurisdiction in which the alleged conduct has occurred.” Asked about the allegation against a cabinet minister, a spokesperson for the prime minister referred to the AFP advice that “reporting to the police is the way to ensure any alleged crimes are properly investigated”. They declined to answer further questions about the historical rape allegation, citing Kershaw’s warning that “choosing to communicate or disseminate allegations via other means, such as through the media or third parties, risks prejudicing any subsequent police investigation”. A spokesperson for the AFP said it would “not be commenting on this matter”. The South Australia police said on Friday night “it is a matter for the coroner and SA police will not be making any further comment at this time”. • In Australia, support is available at 1800Respect (1800 737 732). In the UK, Supportline can be reached on 01708 765200. In the US, Rainn offers support on 800-656-4673. Other international helplines can be found at ibiblio.org/rcip/internl.html