The prime minister was briefed on February 24 about the claims, which are strenuously denied by Christian Porter.

Mr Kershaw faced questions about the briefing at a parliamentary hearing on Monday, with Labor's Kristina Keneally asking if it was appropriate.

He said the seriousness of the allegations and an active criminal investigation in NSW contributed to his decision to speak with Mr Morrison.

"I made my judgment based on those matters and the fact you're dealing with a senior member of parliament," Mr Kershaw told the Senate hearing.

The briefing included the nature of the allegation, he added.

It also covered general details about jurisdictional issues in NSW where an investigation was ongoing, and South Australia where the coroner was looking at the woman's death.

The commissioner also revealed federal police did not immediately send a dossier detailing the allegations to NSW counterparts because it wasn't requested.

Mr Kershaw said the AFP wanted to put the material through its own internal processes and therefore provided a detailed summary to NSW Police.

The dossier reportedly contains detailed information about the 1988 alleged incident which Mr Porter says never happened.

NSW Police announced the investigation would not proceed because of a lack of admissible evidence.

Mr Kershaw said state police did not request the dossier which was later passed on after it was determined to be outside of the AFP's jurisdiction.

Finance Minister Simon Birmingham said the government sought the solicitor-general's advice about trimming Mr Porter's responsibilities after he initiated defamation proceedings.

Mr Porter is seeking aggravated damages from the ABC and journalist Louise Milligan over stories related to the allegations.

The solicitor-general is expected to provide advice about the attorney's portfolio this week ahead of Mr Porter's return from medical leave next Wednesday.

Senator Birmingham confirmed Mr Porter was receiving his full ministerial salary during his leave.

The finance minister said Mr Morrison didn't read the dossier but did know the complainant's name after being briefed by the police commissioner.

"The prime minister believed he was following appropriate processes," Senator Birmingham told a hearing.

But Labor's Penny Wong questioned how Mr Morrison could assert Mr Porter's innocence without reading the detailed allegations.

"The police don't decide who gets to be in cabinet, the police don't decide who gets what role," she said.

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