There were fears confidential submissions detailing sexual assaults and harassment could become public if subject to Freedom of Information requests, discouraging current and former staffers from telling their stories to the review by Sex Discrimination Commissioner Kate Jenkins.

Passed unanimously, the bill was introduced almost 24 hours after a letter was sent to Mr Morrison and Labor leader Anthony Albanese, from dozens of current and former staffers from across the political divide calling for the change to protect them when they share personal stories of assault and harassment.

"This legislation provides participants, whether that be current or former staff, or anyone else, with the assurance that if they make a submission or participate in any way, that if they wish for their participation to remain confidential that it will remain so," Finance Minister Simon Birmingham said.

"We have always had strong confidence that using the Australian Humans Right Commission for this Review would provide sufficient protections to guarantee confidentiality, and this legislation now provides an absolute additional layer of assurance."

Prime Minister Scott Morrison said the government and opposition had agreed to a measure that would hopefully provide comfort and security to people to make submissions.

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Ms Jenkins has been commissioned by the government to undertake a review into the culture of parliamentary workplaces, following the allegation by former Liberal staffer Brittany Higgins that she was raped in the office of Defence Minister Linda Reynolds, and felt she couldn't report it without losing her job.

"There is currently no guarantee that information submitted will remain private as it would if the inquiry were conducted under parliamentary privilege," the letter from the former staffers, including Brittany Higgins, Jamila Rizvi and Fiona Sugden, said.

The possibility that submissions could be released under Freedom of Information, or released in 20 years under the Archives Act, would discourage contributions, and could increase trauma.

"The Sex Discrimination Commissioner herself has said the review should be victim centred and trauma informed. Any approach made by the Commissioner to those making submissions regarding possible publication of their experiences is neither of those things and could exacerbate trauma," the letter said.

"We are concerned that even if names are redacted, details of submissions could still lead to the identification of victims - or the alleged perpetrators."

The letter was also signed by Therese Rein and Lucy Turnbull.

"We have to give them that right to confidentiality, otherwise it will deter people from coming out," Ms Turnbull told the ABC.

"It is very troubling, even if the term were for 20 years, those people may be on the cusp of becoming Prime Minister of Australia, either complainant or perpetrator, who is an alleged perpetrator who might be cleared. We have to clean the whole thing up so it can't come back to haunt them later on."

Ms Rein said the report wouldn't be fully informed if staffers felt they couldn't make submissions because they wouldn't be confidential.

"For Kate Jenkins to be able to do her review, she needs frank and fearless information about what's been happening and the scale of what has been happening so that she can make recommendations about what new systems and processes need to be put in place so that people can feel safe and confident and comfortable," she said.

At the time the review was announced, Ms Jenkins said first-hand experiences would be critical to building a safer, more equal workplace.

"We recognise the significant public interest in this issue and the need to ensure matters will be treated with sensitivity, confidentiality, and be trauma-informed," she said at the time.

"I urge every staff member to share their experiences with us via a written submission or interview."

As well as hearing from staff and politicians on how to make cultural changes to prevent assault, harassment and bullying, the review will also assess whether existing frameworks and legislation promote or impede safe and respectful workplaces.

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