Scott Morrison has again ruled out calling an independent inquiry into rape allegations against Attorney-General Christian Porter.
The prime minister argues the allegations should be dealt with through the police and the courts.
"I see no justification for any extrajudicial inquiry that might be set up by a prime minister or any other politician," he said on Tuesday.
"We have competent and authorised agencies to deal with these matters both through the police and the courts, and that is where I will make my assessments of those matters. That is where it should be done."
Mr Porter has taken indefinite leave after vehemently denying he raped the woman more than 30 years ago.
Asked whether he believed the denial, Mr Morrison said he believed in the presumption of innocence and the rule of law.
"There are not two rules, there are not two laws in this country, there are not two processes, there is one and we are all subject to it," the prime minister said.
"I'm not going to indulge in other extrajudicial processes that suggest that one Australian is subject to a different legal process to any other Australian.
"If we do that, we are eroding the very principles of the rule of law in this country. So, there are not two laws in this country and I won't allow that to be eroded."
The South Australian woman who made the claim took her own life last year after telling NSW Police she did not want to proceed with her complaint.
Employment Minister Michaelia Cash, who is filling in for Mr Porter, says the rape allegations against him should not be investigated further.
"Once the police have closed an issue like this, that is actually where the matter stops," Senator Cash told Nine.
"The NSW Police have made it very clear - the matter is closed. They are not pursuing it any further."
Former cabinet minister Julie Bishop says the next logical step is an inquest led by the SA coroner.
While Labor and some of the woman's friends have backed calls for an independent inquiry into the allegations, Ms Bishop said an inquest was appropriate.
"It's within the criminal justice system. There are checks and balances and there are statutory powers," she told the ABC's 7.30 Report on Monday.
"It has legal standing. And so, that is the next step and I understand from media reporting that's what the family would welcome."
Federal minister Anne Ruston also backed an inquest but said it was up to the coroner to make an independent decision.
"I think everybody will be happy if the coroner in South Australia decides to investigate," she said.
Mr Morrison is open to a coronial inquest.
"If there should be coronial inquiries, then that of course is the process and I am happy to see those processes proceed as coroners see fit," he said.
But former prime minister Malcolm Turnbull said an independent inquiry would be in the best interest of Mr Porter.
"That would enable there to be a process which would enable the issue to be resolved. The problem is it remains unresolved in the minds of many people," Mr Turnbull said.
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