NSW Treasurer Matt Kean says "horrible cowards" forced Dominic Perrottet's confession about wearing a Nazi costume to his 21st birthday party, and has challenged them to come forward.
The premier remains under pressure after admitting to wearing a Nazi uniform to the event in 2003, at a press conference last week.
His public apology came after a phone call with Transport Minister David Elliott last Tuesday, who advised Mr Perrottet rumours were being spread about the party.
Today, the premier and treasurer were again asked about the saga at a media call marking the start of the state government's new land tax scheme.
Last week, it was revealed Mr Elliott was the first to raised the issue of the costume with Mr Perrottet, but it is unclear who else knew about the uniform, and whether they were trying to trash the premier's reputation.
"Well I don't know who it is," Mr Kean said when asked if there were people within the Coalition conspiring against Mr Perrottet.
"But these horrible cowards should come out from the swamp that they're living in and put their name to these horrible smears.
"These people should have no place in Australian public life. They want to play their silly games. Well, we're not going to indulge that."
It remains unclear if a photo of Mr Perrottet wearing the costume exists.
Mr Kean rejected assertions he was "potentially" calling members of his own government cowards, and that the government was disunited ahead of March's state election.
"What I said was whoever is doing these things should put their name to it, should come out, rather than hiding anonymously behind a keyboard pushing smear," he said.
"That's not acceptable.
"Put your name to it. Have some courage. Stop being a coward."
Mr Perrottet said he was not concerned about Shooters and Fishers Party leader Robert Borsak's moves to refer the premier to police.
Mr Borsak is also referring the matter to parliament's public accountability committee, saying it should probe whether Mr Perrottet disclosed the Nazi outfit incident during his vetting process for pre-selection.
Mr Kean also leapt to the premier's defence against Mr Borsak's allegations, claiming their political opponent had "no credibility on this issue or anything else".
