Dozens of prominent lawyers have signed a formal complaint seeking the suspension of Rudolph W. Giuliani’s law license — the latest and loudest in a series of calls to censure him for his actions as President Donald J. Trump’s personal attorney.

The lawyers said Mr. Giuliani had trampled ethical boundaries as he helped Mr. Trump pursue false claims of election fraud, then gave an incendiary speech repeating those claims just before the riot at the Capitol on Jan. 6.

A draft of the complaint to the Supreme Court of New York’s attorney grievance committee accuses Mr. Giuliani of knowingly making false claims about the election and urges an investigation into “conduct involving dishonesty, fraud, deceit or misrepresentation in or out of court.”

Calls to discipline Mr. Giuliani have mounted in the weeks since the riot and are intensifying even now, after Mr. Trump has left office. The latest complaint, signed by a bipartisan who’s-who of legal luminaries from New York and beyond, represents perhaps the most serious condemnation of Mr. Giuliani’s conduct to date.

The list included former acting U.S. Attorney General Stuart M. Gerson, former U.S. district judges H. Lee Sarokin and Fern M. Smith, and two former state attorneys general, Scott Harshbarger of Massachusetts and Grant Woods of Arizona. Also signing the complaint were prosecutors who worked in the same United States attorney’s office for the Southern District of New York that Mr. Giuliani led during the 1980s, including Christine H. Chung.

Ms. Chung, a steering committee member of Lawyers Defending American Democracy, the organization that filed the complaint, said that the group had reviewed the work that Mr. Giuliani did on Mr. Trump’s behalf, and that it amounted to “a purposeful campaign to go to the American people with a lie about a stolen election.”

“This is a man that once led the highest prosecuting offices in this nation, and he knows what fraud is, and what it’s not,” said Ms. Chung, who did not work for the U.S. attorney’s office during Mr. Giuliani’s tenure. She added, “For a lawyer to be attacking the rule of law is disallowed, and it’s dangerous.”

Ms. Chung said that by Thursday evening more than 1,000 people had signed the complaint, which anyone can sign on Lawyers Defending American Democracy’s website, and that she expected “thousands” more to add their names.

The complaint, which calls to suspend Mr. Giuliani’s license to practice law during an investigation into his conduct, is one of several that have been filed with the grievance board. It comes a week after New York State Senator Brad Hoylman, the chairman of the State Senate’s judiciary committee, called for the state court system to begin the formal process of stripping Mr. Giuliani of his license to practice law.

Conducting the investigation and deciding on a fitting penalty could take months, or even years, largely because of procedural hurdles and the complexity of Mr. Giuliani’s case, said Stephen Gillers, a law professor at New York University and an expert on legal ethics.

Mr. Gillers said that he hoped the court would conduct a thorough investigation and would suspend Mr. Giuliani’s license while it did so, because Mr. Giuliani had traded on his reputation as a lawyer to promulgate false accounts.

“It’s a privilege and an honor to be a New York lawyer, and by investigating Giuliani and possibly sanctioning him for his behavior the courts reaffirm that fact,” Mr. Gillers said.

Mr. Giuliani, who did not respond to requests for comment, discussed the complaint on his radio show on Thursday afternoon.

“The whole purpose of this is to disbar me from my exercising my right of free speech and defending my client, because they can’t fathom the fact that maybe, just maybe, they may be wrong,” Mr. Giuliani said.

He went on to detail what he described as evidence of his accusations of fraud, and to claim that all his statements were based in fact. He called the complainants “idiots,” “malicious left-wingers” and “irresponsible political hacks.”

“You want to disbar me?” Mr. Giuliani asked. “I think I’m going to move to disbar you.”

The slew of calls for disciplinary action underscores how much Mr. Giuliani’s reputation has changed from his years as a federal prosecutor known for taking on organized crime and his two terms as the mayor of New York City, during which he championed law enforcement and emphasized cleaning up the streets.

At Mr. Trump’s rally on Jan. 6, not long before a violent mob stormed the Capitol, Mr. Giuliani called for a “trial by combat” to address discredited claims of voter fraud.

“I’m willing to stake my reputation, the president is willing to stake his reputation, on the fact that we’re going to find criminality there,” Mr. Giuliani said.

The complaint accuses Mr. Giuliani of sticking to his false accusations of widespread voter fraud as recently as Sunday, sacrificing his reputation in the process.

“Other lawyers observed ethical obligations by stepping back from representing Mr. Trump and his campaign,” the complaint reads. “Mr. Giuliani not only lent his stature and status as a lawyer to the venture but shows no inclination to stop lying.”

Earlier this week, a person close to Mr. Trump said that Mr. Giuliani would not participate in Mr. Trump’s defense during his second impeachment trial in the Senate.

Azi Paybarah contributed reporting.