Senator Linda Reynolds is suing Brittany Higgins for aggravated damages over an Instagram post.
The Liberal Senator, who had threatened the action weeks ago, filed a writ filed in the Western Australian Supreme Court on Monday.
Higgins claimed on Instagram in July that Senator Reynolds “continues to harass me through the media”.
She wrote that her former boss needed to “stop”.
The lawsuit also claims Higgins’ social media activity was a breach of a March 2021 deed settlement which included a non-disparagement clause.
Reynolds is seeking two injunctions that would stop Higgins from further breaches of the deed.
Senator Reynolds first threatened legal action in July.
“Ever since Ms Higgins first made her allegations of rape public, I have been the target of unwarranted criticism and abuse,” she told Sky News at the time.
“Despite her repeated defamation of my character, until now I have not taken any action against her personally - even though I considered her words to breach our previous settlement agreement.
“Yesterday Ms Higgins made yet another defamatory post about me. I have had enough. I will not tolerate being defamed by her or anybody.”
Higgins has since deleted her Twitter account.