Independent MP Alex Greenwich will launch defamation action against One Nation's Mark Latham over a graphic, homophobic tweet.
Mr Greenwich previously warned that he would commence legal proceedings unless Mr Latham apologised, and attempted to make amends.
The New South Wales One Nation leader, who was re-elected in March, had a deadline of 17 days, which expired at midnight on Wednesday.
Late yesterday, Mr Greenwich received a letter from Mr Latham's lawyers saying they would not accept his offers to resolve the situation outside of court.
The offensive tweet was posted seven weeks ago, and the ABC has chosen not to reveal the highly graphic contents.
It has since been deleted from Mr Latham's account.
In a statement, Mr Greenwich said he was not entering in the legal proceedings "lightly".
"Mr Latham’s homophobic, sexualised attack has exposed me to contempt, ridicule and extreme abuse, based on my sexuality, and demands actions," he said.
"It’s 2023 and LGBTQIA+ Australians shouldn’t have to put up with abuse that targets our sexuality, character, or ability to do our jobs."
Mr Latham was responding to Mr Greenwich calling him "a disgusting human being" after LGBTQI protesters were attacked outside a forum Mr Latham was addressing, during the state election campaign.
The One Nation MP then doubled down on those comments.
In a statement on his Facebook page, Mr Latham said he has reported Mr Greenwich to police over the response to the protest incident.
"Alex Greenwich MP used his social media to attack all aspects of my life (as a human being) as extremely dangerous and disgusting," he said.
"This was a reckless, ill-informed and malicious attack on everything I do: my love of my children, my sexuality, my work in the community in which I live and my role as a NSW parliamentarian."
Widespread condemnation of tweet
The homophobic tweet has been widely condemned by all politicians, including One Nation Leader Pauline Hanson.
Premier Chris Minns has said Labor will not work with Mr Latham, who is a key crossbench member in the Upper House, while Opposition Leader Mark Speakman has vowed to work with everyone in parliament, including Mr Latham.
Mr Greenwich has made a formal complaint to police against the One Nation MP, for using a carriage service to harass and offend, and has also lodged a complaint of homosexual vilification to the anti-discrimination board.
Those investigations are ongoing.
When the Independent MP announced this course of action, he said he was doing so because "enough is enough".
"I've been openly gay in public life for 15 years and in parliament for over 10 years, and never have I experienced such a homophobic, sexualised attack that exposed me to contempt, ridicule and extreme abuse, based on my sexuality," Mr Greenwich said.
Parliament returned last week and both Mr Latham and Mr Greenwich were there, but as members in different chambers.
Mr Latham has been re-elected for an eight-year term.
The ABC has approached Mr Latham for comment.
