The Office of Disciplinary Counsel, the disciplinary arm of the Columbia Bar Association, has sued the former federal prosecutor and the mayor of New York City, alleging that it sponsored unfounded allegations of voter fraud in Pennsylvania. The lawsuit was filed on June 6, and published on Friday.

The dispute revolves around Mr. Giuliani’s allegations of supporting a lawsuit brought by Mr. Trump’s campaign to nullify the results of the Pennsylvania state election. That lawsuit, which sought to invalidate up to 1.5 million mail-in ballot papers, was rejected by the courts.

The Office of the Board said Mr. Giuliani’s conduct violated the Pennsylvania Code of Ethics “in that he initiated a lawsuit in which he asserted that there were unfounded and non-absurd matters of law and did ‘do so’ and that he engaged in conduct prejudicial to the administration of justice.”

The Board requested to hear the District Court of Columbia Appeals Committee on Professional Responsibility in the case. According to the filing, Giuliani has 20 days to respond. It was impossible to speak to a lawyer for Mr. Giuliani on Saturday.

The move is the latest against Giuliani for his role in Donald Trump’s overt allegations that the 2020 presidential election was fraudulent.

Last June, an appeals court suspended him from practicing law in New York for making false statements while trying to get the courts to annul the incumbent’s defeat. A disciplinary panel for lawyers asked the court to suspend his license on the grounds that he had violated the code of professional conduct by promoting theories that elections had been stolen by fraud.

The District Bar Association was temporarily suspended last July, although the practical implication of the measure is debatable, given that Mr. Giuliani’s license to law in Washington has been inactive since 2002.

The House’s new move follows the first public hearing of the House committee investigating the Capitol riots on January 6, 2021. Rudy Giuliani met the committee for hours last month.