Sydney MP Alex Greenwich says he has lodged a complaint with NSW Police and the state's anti-discrimination board about what he describes as "homosexual vilification" from One Nation leader Mark Latham.
Mr Latham published a graphic, homophobic tweet appearing to target Mr Greenwich and the LGBT community on March 30.
The tweet is now deleted, and the ABC chose not to publish it.
In a statement, Mr Greenwich said unless Mr Latham "apologises and makes amends" he would also commence defamation proceedings against him.
Mr Greenwich, an openly gay man who is married to his long-term partner, says the complaint to the Anti-Discrimination Board of NSW is for "homosexual vilification".
The complaint to NSW Police is for using a carriage service to menace, harass, or offend, the statement reads.
NSW Police has confirmed they are now investigating the matter.
"Officers attached to Surry Hills Police Area Command have commenced an investigation after receiving reports of online harassment directed at a 42-year-old man," they said in a statement.
"Inquiries are continuing."
In his statement, Mr Greenwich said Mr Latham's comment was defamatory and homophobic.
"Enough is enough," he said.
"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 says he will also instruct his legal team to approach Twitter "with respect to its provision of a platform that freely allows extreme homophobia, transphobia, racism and religious bigotry."
Mr Latham did not apologise for the comments and continues to tweet about Mr Greenwich.
Amid calls for him to say sorry, Mr Latham, who was returned to the Upper House in the recent state election, indicated he would not back down from his views.
In the days following the comments, he quoted a headline from an online article saying, "never apologise, never explain".
The content of Mr Latham's tweet was widely condemned, including from within his own party's leadership.
One Nation founder and leader Pauline Hanson said she and her party associates did not condone the remarks and she has asked Mr Latham to apologise publicly.
"I think [the comments] are disgusting," she said in a video on Facebook.
Prime Minister Anthony Albanese also condemned Mr Latham for his comments.
Equality Australia, an organisation which advocates for the LGBTQIA+ community, has also denounced the remarks and supported Mr Greenwich's complaints.
Legal director Ghassan Kassisieh said it should not require legal action for a person "to do the right thing, acknowledge the harm they have done and apologise".
Mr Kassisieh said he believes hate speech targeting queer people is becoming more common.
"Such attacks have escalated in recent years, as our lives have become the topics of political debates," he said.
The ABC has contacted Mr Latham for comment.
