A federal judge has tossed out a defamation suit filed against ex-New York Chief Judge Janet DiFiore — who resigned last month amid an ongoing ethics probe — as “implausible to frivolous.”

The lawsuit, first filed by NY State Court Officers Association boss Dennis Quirk in 2020 and revised last year, referenced two Post stories that revealed DiFiore had ordered a racial discrimination probe into the union head over his alleged treatment of black court officers.

Quirk alleged DiFiore and co-defendant Chief Administrative Judge Lawrence Marks fed the “false, defamatory and injurious allegations” to The Post, which was not listed as a defendant.

The union leader had sent a fiery email to DiFiore — who stepped down last month — objecting to the release of the accusations against him, telling her, “[L]et’s see have [sic]you like the online articles about your relationship with a police officer with ties to organized crime while you were married posted all over every court building in NYS.”

The Office of Court Administration subsequently brought disciplinary charges against Quirk for sending a “threatening email to Chief Judge DiFiore designed to intimidate her.”

Upon his suspension, OCA also told The Post that Quirk was suspended for publishing the chief judge’s address on social media. He has since retired as a court officer but remains president of the officers’ union.

Quirk — who had been critical of the court system’s safety measures during the worst of the COVID-19 outbreak — also named state Senate Judiciary Committee Brad Hoylman (D-Manhattan) and Senate counsel Erik Katz in the suit.

He accused them of violating his free speech rights after he wasn’t invited to speak at a legislative hearing on the court system’s response to the pandemic — a claim US District Judge Lewis Kaplan deemed “implausible to frivolous.”

Kaplan, in his 29-page ruling dated Sept. 13, also said Quirk did not prove defamation or retaliation, finding those claims were “meritless.”

He said DiFiore and the judiciary merely called for a probe of Quirk based on a court officer’s email alleging discrimination — and concluded any of their comments had free speech protections.

“It is a fundamental principle of First Amendment law that no one can be liable for expressing their opinion . . . no matter how unreasonable, extreme or erroneous these opinions might be,” the judge wrote.

“It would be an understatement to say that it is at least as plausible that Mr. Quirk was investigated and charged for attempting to intimidate the state’s highest judicial officer than for his COVID-related comments or any combination of other reasons nowhere mentioned in the charging document,” Kaplan said.

An OCA spokesperson for DiFiore and the OCA applauded Kaplan’s ruling.

“Clearly Judge Kaplan found the entirety of the lawsuit to be a paper tiger. It is bizarre and unfortunate that Mr. Quirk continues to use Court Officer’s union resources, financial and otherwise, to further his personal vendetta against senior administrators of the Court System and the former Chief judge,” said OCA spokesman Lucian Chalfen.   

Quirk said he was disappointed with the ruling but said DiFiore is “not out of the woods” given the ongoing ethics probes.

The Commission on Judicial Conduct is reportedly investigating whether DiFiore improperly used her influence to urge court officials to punish Quirk.

Meanwhile, Quirk in August filed a separate ethics complaint against DiFiore with the judiciary calling for officials to strip her of her law license.

That complaint charges that DiFiore improperly intervened in his disciplinary case; refused to comply with court orders when the chief judge was sued by 46 older judges forced out of their jobs; and ruled on cases instead of recusing herself involving the law firm Greenberg Traurig, which personally represented her in the litigation involving the older judges.

Quirk also accused DiFiore of “conspiring” with former Gov. Andrew Cuomo on the appointment of four additional judges to the state Court of Claims to “clear the pathway” for the chief’s daughter, Alexandra Murphy, to run for and be elected to a seat on the state Supreme Court in Westchester County.

“We already forced DiFiore to resign. The Commission of Judicial Conduct and the grievance committee are active cases against her,” Quirk said.

He also said he recently filed a case with the Public Employee Relations Board alleging that DiFiore and OCA meddled in union affairs.

DiFiore, through a spokesman, previously dismissed the disbarment complaint filed by Quirk.