Jobs Minister Michaelia Cash has been forced to withdraw her threat to name "every young woman" in Opposition Leader Bill Shorten's office about whom, she claims, "rumours abound".

Key points: Michaelia Cash was questioned about her new chief of staff

Michaelia Cash was questioned about her new chief of staff She threatened to reveal rumours about women in Bill Shorten's office

She threatened to reveal rumours about women in Bill Shorten's office She was forced to withdraw her threat after being confronted by Penny Wong

Senator Cash made the threat during a tense Senate Estimates hearing in which Labor senator Doug Cameron repeatedly asked the Minister about her newly hired chief of staff and that person's employment record.

The Jobs Minister took issue with the line of questioning, arguing it was unusual to discuss "staff matters" and warned Senator Cameron he was going down a "dangerous path".

"If you want to start discussing staff matters, be very, very careful," she warned.

"Because I am happy to sit here and name every young woman in Mr Shorten's office over which rumours in this place abound.

"If you want to go down that path today, I will do it."

Minister for Jobs Michaelia Cash was told to "settle down". (AAP: Mick Tsikas)

Senator Cameron laughed off the threat and told Senator Cash to "settle down" and take "a chill pill", but the Jobs Minister became increasingly irate.

"Do you want to start naming them for Mr Shorten to come out and deny any of the rumours that have been circulating in this building now for many, many years?" she asked.

"[It's a] dangerous path to go down and you know it."

Senator Cash did not provide any details about the rumours, who they relate to, nor what they are about.

Labor's Wong, Plibersek come back swinging

Soon after the exchange, Labor senator Penny Wong, who was not in the hearing, intervened to demand Senator Cash withdraw the "outrageous slurs … impugning the staff working for the Leader of the Opposition".

Senator Cash then withdrew the comments "if anyone had been offended by them".

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Former prime minister Tony Abbott said he had no idea what Senator Cash was thinking.

He told Sydney radio 2GB he could only assume Senator Cash had a "brain snap".

"I gather she's apologised, she certainly should and let's hear no more of it," Mr Abbott said.

Deputy Opposition Leader Tanya Plibersek blasted Senator Cash for her "attack on the young women in this building" and labelled her comments "ghastly, sexist and a 1950s style throwback".

"Today the Minister for Jobs attacked young women doing their jobs. Today the minister representing the Minister for Women smeared young women," she said.

She said the Minister's "mealy mouthed, conditional" apology was not enough and called on the Prime Minister to make her offer a "proper apology to all of the young women she has offended".

Sorry, this video has expired Tanya Plibersek hits back at Michaelia Cash after criticism of Bill Shorten's staffers

Nadine Flood, the head of the Community and Public Sector Union, called on Senator Cash to resign, saying women around the world are refusing to stay silent about sexual pressure, harassment and assault in workplaces.

"Michaelia Cash has gone the other way by threatening to slur a group of young women," Ms Flood said.

"These slurs are an insult to the young women she threatened to drag through the mud this morning and indeed an insult to all people working in Parliament."

Parliament and private lives

The exchange is yet another example of the change in tone at Parliament House, and increased scrutiny of people's private lives, in the wake of the Barnaby Joyce scandal and overhaul of ministerial standards.

Lines of questioning which would previously have been deemed unseemly are now becoming more common, from Nationals senator Barry O'Sullivan threatening to name MPs having affairs to defence chiefs being quizzed about the relationships of senior military officers.

Senator Cash said she was trying to highlight the fact rumours circulate around Parliament House and are not necessarily true.

But she is also sensitive to questions about her staff after her media adviser tipped off journalists to a raid on the Australian Workers' Union offices last year and was forced to resign as a result.

Her chief of staff quit soon after, but she told Senate Estimates his replacement was "well qualified and has been taken on board because of the skill set they will bring to my office".