NSW independent MP Alex Greenwich will next week file a defamation suit against the NSW One Nation leader, following through on a threat to sue over the tweet posted by Mr Latham in March.
"I know this is not going to be an easy process," he told reporters on Thursday.
"But when someone seeks to reduce you to being a sex act, continues those attacks on you and has a history of attacking the LGBTI community, enough is finally enough.
"I am not willing to take this or ignore this."
Mr Greenwich, a former national convenor of advocacy group Australian Marriage Equality, will ask the court to award maximum general damages, amounting to about $421,000.
He will also seek aggravated damages on the grounds he had suffered ridicule, hatred and contempt.
While Mr Latham has deleted the tweet, he stood by the remark in a subsequent media interview.
In Mr Greenwich's view, Mr Latham had implied he was a danger to children and made repeated attacks based on Mr Greenwich's sexuality.
A concerns notice had not resulted in an apology by Wednesday, prompting the decision to head to the Federal Court.
Mr Latham, through lawyers, disputed his actions were defamatory, Mr Greenwich's lawyer said.
But Nicholas Stewart said his client had experienced the damage of "very dangerous words" and was "constantly attacked" by people with prejudices towards the LGBTQI community and threats
"Words have consequences," Mr Stewart said.
The matter has also been referred to Anti-Discrimination NSW and NSW Police.
Mr Latham responded on Wednesday by referring Mr Greenwich to police for possible harassment offences.
The report related to comments about riot police dispersing hardline Christian groups who had encircled LGBTQI protesters outside a church in March.
Mr Latham had been invited to the church hall meeting to speak on religious freedom and parental rights.
"Alex Greenwich MP used his social media to attack all aspects of my life (as a human being) as extremely dangerous and disgusting," the former Labor leader posted to Facebook on Wednesday.
"Greenwich misused his carriage services in his attacks on me, saying that I had deliberately incited violence. In truth, I consistently condemned the violence."
Mr Greenwich cast his comments as a reasonable expression of his opinion on a specific event.
Police on Thursday confirmed a report had been received by Surry Hills officers and inquiries were continuing.
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