Senator Reynolds on Sunday extended her medical leave until April 2, meaning she will miss the next sitting of parliament and a week of gruelling Senate estimates hearings.

She has been under pressure over her handling of former Liberal staffer Brittany Higgins, who publicly alleged she had been sexually assaulted by a colleague in the minister's office in 2019.

The case is now being investigated by police after Ms Higgins lodged a formal complaint.

The defence sector is facing a number of complex issues including the future of the $90 billion submarine program and the Afghanistan war crimes investigation.

Labor leader Anthony Albanese said Senator Reynolds should have resigned over calling Ms Higgins a "lying cow" and her handling of the sexual assault complaint.

"It sends all the wrong messages to women who are brave enough to come forward," he told reporters in Sydney on Monday.

"Linda Reynolds' position is simply untenable."

Acting defence minister Marise Payne said work was continuing in the portfolio area.

She said it was unreasonable for someone on medical leave to be facing calls to resign, arguing senior business executives would be allowed to deal with the health issue.

"That same respect and that same acknowledgement should be extended to minister Reynolds in these circumstances," Senator Payne told reporters.

Former Labor defence minister Joel Fitzgibbon said while he had great empathy for Senator Reynolds, there were big national security challenges at play.

"We need a defence minister at work," he told the Seven Network.

"We have enormous changes happening in our region, she hasn't handled the report into our special forces well at all, she hasn't really stood by our troops.

"We have projects like the submarine program, excuse the pun, sinking."

Social Services Minister Anne Ruston said she was sure her ministerial colleague would be back as soon as her doctor gave her the green light.

"She's in the process of having her condition stabilised by new medication. I'm sure Linda will be back at work as soon as she possibly can," Senator Ruston said.

A review has been launched, headed by Sex Discrimination Commissioner Kate Jenkins, into the way in which complaints of bullying, sexual harassment and sexual assault are handled within Parliament House.

It is expected the final outcome will be a recommendation for a new independent complaints-handling body.

Former independent MP Kerryn Phelps said a "system correction" was needed to ensure complaints could be properly reported and dealt with.

Dr Phelps said a change in political culture would also help.

"It can be done different, where politics doesn't have to be a blood sport, where politics can be a contest of ideas and ideals," she told Sky News.

Australian Associated Press