The Canberra Times has confirmed the unnamed minister has sought advice from defamation expert Peter Bartlett ahead of his first public statements about the allegations which have rocked Federal Parliament.

The development comes as the federal government on Tuesday established a 24/7 confidential hotline for current and former political staffers to report serious incidents.

The new hotline was recommended in a review launched after political staffer Brittany Higgins broke her silence about her alleged rape in Parliament House.

Revelations the minister at the centre of the historic rape allegations is set to make a public statement came after former prime minister Malcolm Turnbull called on the man to identify himself.

Prime Minister Scott Morrison had on Monday said his cabinet colleague had vigorously denied the allegation when he was asked about it.

"He should out himself and he should provide a comprehensive statement about what he knows about the allegations," Mr Turnbull told ABC radio on Tuesday morning.

"If he's vigorously denied the accusations to the Prime Minister, he should vigorously deny them to the public."

Just hours after Mr Turnbull's comments, NSW Police announced it had closed its investigation into the historical alleged crime.

The incident is alleged to have occurred in Sydney in 1988 when the woman was 16.

The woman went to NSW Police last year but the investigation was suspended when she took her own life in June 2020 after telling authorities she didn't want to proceed.

ABC's Four Corners revealed the bombshell allegations late last week after a letter detailing the complaint was sent to Mr Morrison, Greens senator Sarah Hanson-Young and Labor's Penny Wong.

"NSW Police have since sought legal advice in relation to these matters," police said in a statement.

"Based on information provided to NSW Police, there is insufficient admissible evidence to proceed."

Mr Morrison and senior coalition ministers have repeatedly insisted the allegation is a matter for police.

Mr Turnbull said the cabinet minister needed to present a comprehensive explanation of his innocence before resuming his duties.

"It's impossible for him to function in that cabinet," he said.

"Are we seriously going to have a question time where the opposition asks every single minister whether they are the person named in the complaint?"

The new confidential complaints hotline set up on Tuesday was an interim recommendation from one of the reviews launched in the wake of the Brittany Higgins allegations, Finance Minister Simon Birmingham said.

The review is being conducted by the deputy secretary of the Department of Prime Minister and Cabinet, Stephanie Foster.

"Every Australian has a basic right to feel safe in their workplace," Mr Birmingham said.

"I encourage current and former Commonwealth Parliamentary employees who have experienced a serious incident in the Parliamentary workplace, or who have been affected by the allegations of serious crimes in the past fortnight, to make use of this private and confidential new service."

Chrystina Stanford from the Canberra Rape Crisis Centre said the new hotline was an option that wasn't there before and people needed choices.

"It depends on what happens after that, what access to support and, in the longer term, justice do they have as a result of that?" Ms Stanford said.

Whether it is a success will depend on how it links together with police, rape crisis centres and other services in the jurisdictions, she said.

- with AAP

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