Prime Minister Malcolm Turnbull has backed his Jobs Minister Michaelia Cash, saying she was being "bullied and provoked" when she made extraordinary remarks about the Opposition Leader's staff.

Key points: Senator Cash "unreservedly" withdraws her Senate Estimates remarks

Senator Cash "unreservedly" withdraws her Senate Estimates remarks A Liberal Senator indicates she was uncomfortable with Senator Cash's comments

A Liberal Senator indicates she was uncomfortable with Senator Cash's comments Independent MP Cathy McGowan says Federal Parliament should have code of conduct

During a heated Senate Estimates hearing yesterday, Senator Cash threatened to reveal unverified rumours about female staff in Bill Shorten's office.

In the Lower House, Mr Shorten kicked off Question Time by asking Mr Turnbull whether he would direct Senator Cash to apologise and "send a clear message of support to all of the staff who work in this building".

Mr Turnbull told the Chamber, Senator Cash had withdrawn the remarks that were made during a "very heated exchange".

"She was being bullied and provoked by [Labor] Senator [Doug] Cameron … who was making insinuations about staff," he said.

"She has withdrawn those remarks and withdrawn them unreservedly."

Jobs Minister Michaelia Cash has now "unreservedly" withdrawn her contentious remarks. ( ABC News: Andrew Kennedy )

Senator Cash had not — she said on Wednesday that she withdrew the remarks "if anyone had been offended by them" — but soon after Question Time on Thursday, she made a full retreat.

"I withdrew the comments yesterday and I am more than happy to withdraw them unreservedly," she said.

The senator's office has written a formal complaint about being filmed entering a Senate Estimates hearing at Parliament House but denied asking for the whiteboard to be used.

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Coalition MPs have largely closed ranks around Senator Cash but Liberal senator Lucy Gichuhi, who was chairing yesterday's committee meeting, indicated she was uncomfortable with the exchange.

Asked whether she was surprised by Senator Cash's comments, Senator Gichuhi simply said, "well … well… next question" as she laughed and walked off.

Earlier on Thursday, Labor senator Kim Carr was forced to apologise and withdraw his remarks after suggesting Liberal senator James Paterson would have been part of Hitler's Youth movement.

Mr Turnbull described Senator Carr's comments as "disgraceful" and in another Senate Estimates hearing, Liberal Jane Hume warned her Labor colleagues to "tread lightly" in their questioning.

"The Opposition hasn't shrouded itself in glory this week and you won't be getting vertigo from the moral high ground after Senator Carr's comments," she said.

Sleaze and mud slinging demand code of conduct: McGowan

Independent MP Cathy McGowan says the sexual rumours, innuendo and personal attacks mean it is time for Federal Parliament to instigate a code of conduct.

Barnaby Joyce's extra-marital affair and the ensuing atmosphere of sleaze and mud slinging that has engulfed federal politics in recent weeks has prompted a rethink.

"The community does have expectations of how politicians behave … that you be honest, that you be trustworthy, that you don't tell lies, but they're not encoded," Ms McGowan told the ABC.

Last month, the Prime Minister strengthened the code of conduct for ministers, but there is nothing similar for MPs.

"I had absolutely assumed that there would be principles that you'd sign up to, there is for the ministers, but there's not for ordinary members of Parliament," Ms McGowan said.

She said she was not only focused on cracking down on sex between politicians and their staff.

"It really is about a code of conduct across a whole way of being … would it be principle-based or would it be activity-based is still the discussion we've got to have yet," Ms McGowan said.

The behaviour of politicians has dominated the media cycle in recent weeks.

Senator Paterson has conceded federal politics is at its lowest ebb in years, following the scandal with Mr Joyce and days of ugly exchanges in Senate estimates.

Ms McGowan said a code of conduct presented to parliament six years ago did not progress, but should be revived.

"All businesses that I know have a code of conduct around behaviour … we really should be doing something in Australia and now's the time to have the discussion," she said.

Ms McGowan, whose idea draws on codes in the United Kingdom and Canada, wants the Lower House to debate a motion on her proposal when next it meets.