Sydney MP Alex Greenwich will take legal action against Mark Latham unless the NSW One Nation leader apologises for homophobic comments directed at the independent.

Despite widespread condemnation, the maverick One Nation MP has refused to apologise for a tweet he posted on March 30 that Mr Greenwich described as “defamatory and homophobic”.

“He followed that up with media commentary that doubled down on his attack,” Mr Greenwich said on Monday.

The comments were in response to Mr Greenwich calling Mr Latham “a disgusting human being” after LGBTQIA+ protesters were attacked outside a candidates’ forum including Mr Latham as a speaker, during the NSW election campaign.

When pressed for an apology, Mr Latham tweeted “never apologise, never explain”.

Mr Greenwich said unless Mr Latham apologised and made amends, he would begin defamation proceedings.

Mr Latham doubled down on the comments during an appearance on TNT Radio last week.

Mr Greenwich said he did not take the action lightly but it was time someone stood up to Mr Latham, saying “enough is enough”.

“He made a very sexualised, targeted attack at me on Twitter, seeking to impugn my reputation amongst colleagues, and he has since said that he believes that that’s a view that all straight men believe,” Mr Greenwich told reporters on Monday.

“He has continued to make comments around whether it is appropriate for me to talk about my sexuality, whether I am in any way possibly considered to be a threat to children.

“Rather than retracting or apologising, Mr Latham continues to reinforce what I consider to be extremely defamatory, vilifying language, directed at me.”

Damages could be substantial, Mr Greenwich’s lawyer, Nicholas Stewart told reporters.

“After Mr Latham published that tweet, Alex was the subject of ridicule, hatred and contempt,” he said.

“This matter is significant – it’s actually really serious what Alex has experienced.”

The tweet caused a schism between Mr Latham and One Nation’s federal leader Pauline Hanson, who said the comments were “disgusting” and called on him to apologise. She said he ignored her calls and texts.

Last week, Mr Latham denied there had been any contact from Senator Hanson. He told TNT radio host Chris Smith he was speaking for “for straight men”, adding “this is what makes us straight”.

“Pauline hasn’t rung me at any stage during this. I’ve had no contact from her,” he said.

“I’m assuming that, as a woman, she doesn’t understand how straight men feel about this, and I don’t think gay men would understand how straight men feel about it.

“That’s just the reality. And that’s not homophobia, that’s just nature.”

Premier Chris Minns condemned Mr Latham’s comments, saying they were “terrible” and would “unleash ghouls” on the MP. Mr Greenwich said Mr Minns had been a “great personal support” to him.

Prime Minister Anthony Albanese also condemned the comments.

Mr Latham was re-elected for an eight-year term in the NSW upper house in March.

But the legal action could impact his ability to serve if he is charged with an offence by police.

Mr Latham has been contacted for comment.

– with AAP