A legal ethics committee in Washington that oversaw a disciplinary case late year against Rudolph W. Giuliani recommended on Friday that he be disbarred for his “unparalleled” attempts to overturn the 2020 election in favor of his client at the time, President Donald J. Trump.

In its recommendation, the panel from the D.C. Bar’s board on professional responsibility said that Mr. Giuliani’s efforts to “undermine the integrity” of the election had “helped destabilize our democracy” and “done lasting damage” to the oath to support the U.S. Constitution that he had sworn when he was admitted to the bar.

While the panel acknowledged a record of public service by Mr. Giuliani, a former New York City mayor and U.S. attorney in Manhattan, it also noted that “all of that happened long ago.”

“The misconduct here sadly transcends all his past accomplishments,” the panel wrote. “It was unparalleled in its destructive purpose and effect. He sought to disrupt a presidential election and persists in his refusal to acknowledge the wrong he has done.”

Mr. Giuliani’s hearing in front of the ethics committee took place in December and focused on the role he had played in bringing a lawsuit in Federal District Court in Philadelphia that sought to delay the certification of the election results in Pennsylvania.

The federal judge who heard the Pennsylvania case dismissed it, likening it to a “Frankenstein’s monster” that had been “haphazardly stitched together.” A federal appeals court then upheld the dismissal in a scathing order by a Trump-appointed judge who noted that “calling an election unfair does not make it so.”

The legal ethics committee in Washington determined that Mr. Giuliani had filed the suit “when he had no factual basis, and consequently no legitimate legal grounds, to do so.”

“He claimed massive election fraud but had no evidence of it,” the panel wrote. “By prosecuting that destructive case Mr. Giuliani, a sworn officer of the court, forfeited his right to practice law.”

A local court of appeals in Washington will ultimately decide whether to revoke his license to practice law in the city. He has already had his license suspended in New York. One of his lawyers, Barry Kamins, said he was disappointed in the committee’s recommendation in Washington and would file “a vigorous appeal.”

The ethics committee’s recommendation was the latest example of bar authorities seeking accountability for lawyers who tried to help Mr. Trump overturn the results of the election and maintain his grip on power.

In March, under a negotiated agreement with state bar officials in Colorado, the lawyer Jenna Ellis acknowledged that she had knowingly misrepresented the facts in several of her public claims that widespread voting fraud led to Mr. Trump’s defeat. Ms. Ellis worked closely with Mr. Giuliani in various attempts to keep Mr. Trump in office.

Another lawyer who took part in those attempts, John Eastman, is currently facing a disciplinary hearing by bar officials in California that could lead to the loss of his law license. Mr. Eastman, a law professor, was the architect of a plan to pressure Vice President Mike Pence to use his position as president of the Senate to unilaterally throw the election to Mr. Trump during a joint session of Congress on Jan. 6, 2021.

Possible disbarment is not the only legal problem confronting Mr. Giuliani. Late last year, he received a grand jury subpoena from federal prosecutors who are mulling criminal charges related to Mr. Trump’s various attempts to stay in power.

Last month, Mr. Giuliani sat for an interview with prosecutors working for the special counsel Jack Smith, who is leading the election interference inquiry.