The NAACP is pressing San Francisco District Attorney George Gascón to investigate the vote by six supervisors to appoint Mark Farrell mayor, saying it violated city and state laws.

In a complaint sent to Gascón, the city’s Ethics Commission and the city’s Sunshine Ordinance Task Force, Amos Brown — who leads the NAACP’s San Francisco chapter — alleges that a majority of the Board of Supervisors held secret meetings to plot the vote, breaching a state law that requires such discussions to be noticed and open to the public.

Brown cited the state’s Brown Act, under which public officials are barred from holding a series of private one-on-one meetings that lead to a majority vote or legislative action. His complaint hinged largely on reporting by The Chronicle that documented the meetings between Farrell and the board’s progressives.

“This clique got together — the so-called progressive liberals,” Brown said in an interview Wednesday, during which he fulminated against the six supervisors — progressives Hillary Ronen, Sandra Lee Fewer, Jane Kim, Aaron Peskin and Norman Yee, and swing vote Jeff Sheehy — who unseated acting Mayor London Breed, an African American woman.

Breed took over after Mayor Ed Lee’s unexpected death in December, serving simultaneously as acting mayor and president of the Board of Supervisors. The progressives said her dual roles were inappropriate because they interfered with the separation of powers in city government.

Brown accused the supervisors of carefully orchestrating every detail of the Jan. 23 vote to appoint Farrell mayor and remove Breed from the position, for which she is now running in the June election. Brown backs Breed in the race and has appeared at her fundraising events.

“Indeed, at the board meeting that evening, all six supervisors played their roles to perfection,” Brown wrote in his complaint. He said the progressives had anticipated blowback for replacing an African American woman with a white man, which may explain some of their theatrics before the vote, he wrote.

Brown pointed to Fewer’s gesture of also nominating Kim, an Asian American woman, who promptly declined the nomination and said that she had wished to appoint another woman of color, city administrator Naomi Kelly. Those motions, coupled with Ronen’s speech calling out the influence of rich white men in City Hall, were all “choreographed” as political cover, Brown wrote.

“They were a political gang that got together and blocked this young lady, London Breed, from filling her seat,” Brown said Wednesday.

He went on to accuse the “progressive liberals” of City Hall of refusing to share political power with black people. Brown noted a historical pattern, saying “the same gang” had been at odds with San Francisco’s first African American mayor, Willie Brown, who is now a Chronicle columnist.

“Something stinks about that situation,” the NAACP leader said.

None of the six supervisors who voted to appoint Farrell returned phone calls on Wednesday.

Farrell characterized the NAACP complaint as a form of political posturing.

Many of Breed’s supporters have made the vote a theme of the mayor’s race, placing it against the backdrop of the #MeToo movement. They paint Breed as an outsider who was unfairly kneecapped by her colleagues.

In a statement Wednesday, Farrell questioned that narrative.

“Some might think it’s good election-year politics to constantly relitigate the vote in January, but I believe San Franciscans want the mayor focused on the central issues facing the city, from homelessness to public safety to clean streets, and that is exactly what I am doing,” he said.

Ronen echoed those sentiments.

“It’s time to move on,” she said in an interview Wednesday afternoon. “We legally completed our duty under the City Charter, we appointed an interim mayor, we didn’t violate any laws. Now let’s talk about the real issues that voters care about.”

But free-speech attorney David Snyder, executive director of the nonprofit First Amendment Coalition, said the NAACP may have a viable case.

“If what the letter describes is accurate ... then six members of the board communicated to one another about a decision they wanted to make and set forth a plan,” Snyder said. “Doing that is against the Brown Act’s requirements that ... the public be able to see, hear and participate in the deliberation process.”

A spokesman for Gascón said the district attorney had received the complaint but would not comment further. There was no immediate comment from the Ethics Commission.

Brown also requested an investigation by the city’s Sunshine Ordinance Task Force, which probes alleged violations of public records laws. Its president, Bruce Wolfe, said he cannot comment on a complaint before it is deliberated in a public hearing.