WYNN RESORTS on Monday threatened a lawsuit against Boston Mayor Marty Walsh and the city unless he stops his “campaign of falsehoods” and apologizes to the Las Vegas casino developer.

The letter from Wynn’s outside legal counsel, Barry Langberg, is the latest salvo between the company and Walsh, who have been tangling over Wynn’s plan to build a $1.7 billion casino/hotel project along the border of Boston in Everett. Walsh is suing the Massachusetts Gaming Commission to block its award of a casino license to Wynn and is also threatening to withhold permits Wynn needs to upgrade roads in Boston near the proposed facility. Walsh, whose motives are unclear, claims the license was awarded to Wynn through a “corrupt process.”

In his letter to Walsh and his attorneys, Langberg cites “a number of false statements and untrue innuendo about Wynn” contained in the city’s lawsuit and in subpoenas issued last week in connection with the city’s complaint.

“Apparently, you have conducted yourselves with reckless disregard for the truth because you somehow feel your actions are immune from accountability,” Langberg wrote. “Such is not the case. Massachusetts law does not protect individuals (even public officials) from defamation liability for providing falsehoods to the media, even when they attempt to insulate themselves by disseminating the falsehoods in the form of legal documents.” The letter also said the mayor’s actions expose the city of Boston to liability.

A spokeswoman for Walsh says there is no intention of either backing away from the allegations or apologizing to Wynn.

“We dispute the assertions in the letter and we firmly stand behind the allegations in the amended complaint,” Laura Oggeri said in a statement.

Langberg said one of the city’s subpoenas leaked to the press stated that “private investigators working ‘on behalf of Wynn’ obtained ‘unauthorized’ access to police files. This statement is false. Wynn did not employ the named investigators and Wynn has no knowledge of anyone obtaining improper access to police files.” Langberg said the language of the subpoena was “designed to spread vicious falsehoods.”

Langberg said another subpoena alleged that Wynn employees held a meeting where they discussed “the ‘ownership interest’ of a known felon in the land being purchased by Wynn [in Everett]. No such discussion ever took place and the suggestion that Wynn employees knew of and discussed such ownership interest is false and defamatory.”

Wynn officials said they sent Langberg’s letter to city officials on Monday before releasing it to the press. In his letter, Langberg said the city’s complaint against the state Gaming Commission was provided to the media at the earliest possible moment and the subpoenas were leaked to the press even before they were served. He also describes the city’s complaint against the Gaming Commission as “much more a public relations piece than a legal document.”

A hearing on a motion by the Gaming Commission to dismiss the city’s complaint is scheduled for Thursday.

Langberg, the attorney for Wynn Resorts, previously represented Steve Wynn in a slander suit against “Girls Gone Wild” creator Joe Francis, who claimed the Las Vegas gambling executive had threatened to kill him. Langberg, whose law firm is based on Santa Barbara, CA, won a judgment of $20 million plus another $20 million in punitive damages.

Jack Sullivan contributed to this report.

Bruce Mohl oversees the production of content and edits reports, along with carrying out his own reporting with a particular focus on transportation, energy, and climate issues. He previously worked...