Kellie-Jay Keen, also known as Posie Parker, headlined a rally in March 2023 that was gatecrashed by a group of masked men who performed Nazi salutes.
The Let Women Speak rally was attended by then-Liberal MP Moira Deeming, who is also suing John Pesutto after he led a motion to expel her from the parliamentary party.
In a 57-page statement of claim filed in the Federal Court of Australia and obtained by AAP, Mrs Keen accused Mr Pesutto of injuring her personal and professional reputation in a media release and interviews after the rally.
She accused him of having a "reckless indifference to the truth".
The documents claim the media release had several false and defamatory imputations, including that "Keen endorses the views and sentiments of far right-wing extremist individuals and groups including Neo-Nazi activists".
The statement of claim said Mrs Keen is seeking aggravated damages.
It states the pleading was prepared by lawyer Katherine Deves, who was the former Liberal candidate for the Sydney seat of Warringah.
Mr Pesutto said he would defend himself against Mrs Keen's claims.
"I will be vigorously contesting that proceeding and any other proceeding, but I won't be commenting further on it," he told reporters at parliament on Tuesday.
Angie Jones, a co-organiser of the controversial rally, has also confirmed she will launch defamation action against the Victorian Liberal leader.
On Monday, Mr Pesutto said he would not consider standing aside if the proceedings go to trial.
His office released a document outlining contributors to his legal defence that include former Liberal premiers Ted Baillieu, Denis Napthine and Jeff Kennett.
The document does not reveal donation amounts.
