A legal showdown between Liberal Democrats Senator David Leyonhjelm and Greens Senator Sarah Hanson-Young now looks inevitable.
On Wednesday via her lawyer, Ms Hanson-Young sent Mr Leyonhjelm a Concerns Notice demanding he apologise for his recent remarks and pay compensation within seven days or face defamation action.
In response, Mr Leyonhjelm issued a statement on Thursday saying he won't be backing down.
"[Ms Hanson-Young is] wasting her time, money and endless reserves of outrage, because I will not be issuing an apology," he said.
"The thousands of messages I have received in the past four days, from both members of the public and my parliamentary colleagues, have made it clear I have a lot of support."
He said he was "sick of Senator Hanson-Young's confected outrage, her gross generalisations, and her tendency to collapse in a flood of tears when those insults and gross generalisations are bluntly rejected".
Mr Leyonhjelm believed he heard Senator Hanson-Young say in parliament last week words to the effect of "all men are rapists" - which she denies - and responded with "stop shagging men".
He subsequently spread further rumours about her personal relationships in TV interviews.
SBS News talked to Ms Hanson-Young's lawyer Rebekah Giles and has seen a copy of the Concerns Notice.
"This is a matter of principle," Ms Giles said, adding she believed her client had a "very strong case" against Mr Leyonhjelm.
The Concerns Notice sent to Mr Leyonhjelm said he caused Ms Hanson-Young "hurt, distress and embarrassment" over comments he recently made in the media regarding her opinion of men.
It said he had damaged Ms Hanson-Young's reputation by implying she "is a slut, shagging men indiscriminately" and "hates men".
"The imputations are entirely false and defamatory," it said.
It then outlines several conditions that must be met in seven days including "publish[ing] an unreserved apology", "pay[ing] Ms Hanson-Young compensation for the harm suffered" and "pay[ing] Ms Hanson-Young's costs".
Ms Giles said if the conditions were not met - which now seems probable - legal proceedings would commence.
"Taking legal action is a difficult decision... I applaud the bravery of Ms Hanson-Young," Ms Giles said, hinting at the long legal road that could be ahead.
