Former prime minister Malcolm Turnbull has called on the Cabinet Minister at the centre of a historical rape allegation to “front up” in order to clear the reputational cloud now hanging over his colleagues.

His comments come amid growing calls for an independent inquiry into the matter and as confusion reigns about whether a police investigation or coronial inquest into the subsequent death of the woman involved will go ahead.

The story about the toxic culture in Parliament House and the way women are treated in politics has morphed into one that is even more tragic, and which now also poses an existential threat to the Morrison government.

It involves an alleged, most brutal rape of a 16-year-old girl three decades ago – and her death by suicide last year.

The allegation is against a federal Cabinet Minister, and dealing with the allegation is made all the more difficult because neither party has been named.

Mr Turnbull and his wife Lucy received a letter from the woman in late 2019, seeking their advice about what she should do about the alleged assault in 1988.

“It’s a pretty harrowing account,” Mr Turnbull told 7.30.

“But given that she had already engaged a lawyer, who had experience in the area, and was dealing with the New South Wales Police because the alleged offence occurred in NSW, we just confirmed that was the right course of action for her to take. And we didn’t hear any more from her after that. Our response to her confirmed that she was doing the right thing.

“When I learned about six months later that she’d taken her own life, I contacted the South Australian Police Commissioner and forwarded to him her email to us and our response.

“I assumed there would be a coronial inquest.”

Questions over what the PM should do

In forwarding the letter, Mr Turnbull was doing what Scott Morrison last week urged all parliamentarians to do if they became aware of criminal allegations.

But there are further questions about what a Prime Minister should do in these circumstances if the allegation involves one of his own ministers.

Mr Turnbull says one of those questions would be whether the PM would require the Minister who is the subject of the allegation to step down, pending an investigation.

“I think the answer is probably yes, but I’ve got a proviso to that, that sometimes, when an investigation is underway, the police would not want the person being investigated to know that it’s underway,” Mr Turnbull told 7.30.

Former PM Malcolm Turnbull alongside Scott Morrison.(AAP Images/Lukas Coch)

“I think the ball is really in the court of the Minister concerned. I mean, he knows who he is, everyone knows who he is, he may well have known about these allegations for a long time.

“One of the things we don’t know is whether he’d had any communication with the woman who made the complaint.

“There’s a lot of questions to be answered. But the very least the Minister should do and should be called upon to do is to make a full explanation.

“Now, there may be legal reasons why he doesn’t want to do that. But, you know, I think for the sake of his colleagues, the government, everybody — he should front up and state who it is.”

How the historical rape claim could be investigated

The death of the woman has raised question about how an investigation proceeds, or indeed if it can.

As things currently stand, a NSW Police investigation which began in 2020 is now closed, and the South Australian coroner has not announced an inquest almost eight months after the woman’s death.

Aside from a police investigation or a coronial inquiry, barrister Geoffrey Watson says there’s a third option — a private inquiry, initiated by the government and conducted upon appropriate terms in-house.

Geoffrey Watson says the Australian public have a right to know the allegation is being handled properly.(ABC News: Josh Bavas)

“They can all be done concurrently,” Mr Watson told 7.30.

“You can’t underestimate the seriousness of this … a lady is claiming she was raped and then, sadly, took her own life.

“The public really now have got a right to know that this is being handled properly.

“It could well be that through these investigations, the Cabinet Minister’s reputation is cleared. But that’s the process we should be going through.”

Parliamentary inquiry would be ‘appropriate’

Mr Watson says Parliament holding its own inquiry with an independent chair — much like the High Court did over the Dyson Heydon allegations — would be the “best way to go” for the government.

“The greatest lawyers in the land — the members of the High Court — thought that it was appropriate and necessary in that case.

Geoffrey Watson suggests an independent inquiry would be the “best way to go” for the government — much like the High Court did with the Dyson Heydon allegations.(ABC News: Gregory Nelson)

“The involvement of those people who are intimately involved with these events can be protected with appropriate confidentiality, just as it was in the High Court inquiry.”

On Sunday, Liberal MP Sarah Henderson announced that she had forwarded an email she had received about a Labor MP to the police.

Mr Watson says that further strengthens the case for an independent inquiry.

“All of a sudden, the issue is no longer party-political,” he said.

“It just shows you how important it is to have an outsider — not colleagues looking after colleagues — but rather an independent person to look at this across the board.”