Mayor Michelle Wu on Monday formally ended a raucous political brouhaha on Monday when she signed off on a map that redraws the boundaries of the nine City Council districts a year before voters go to the polls for the next municipal election.

The once-a-decade process known as redistricting typically heightens tensions inside City Hall, as councillors are forced to grapple with the gaining and giving up of precincts to create districts that are equal in terms of population and provide opportunities for communities of color to elect candidates of their choice.

As the process approached its finale, this round of redistricting saw one councillor angrily accusing another of anti-Catholic bias in a speech that stunned colleagues and drew gasps from the crowd assembled for last week’s Council meeting. Later in the session, the new map of City Council districts passed by a 9 to 4 vote.

Wu, who over the weekend expressed her disappointment with the tone of the council’s proceedings and the personal attacks in a television interview, signed the measure after a review to make sure it passed legal muster.

The boundaries will be in place between 2023 and 2031.

The lines of Dorchester-based District 3, represented by Councillor Frank Baker, have shifted north, deeper into South Boston. On the new map, the district picks up public housing developments from South Boston-based District 2 and hooks left by picking up the precinct of the Ink Block complex, the former home of the Boston Herald that now comprises residences and a Whole Foods operation.

As to subtractions, District 3 lost the precincts along the Neponset River and in Adams Corner, including Ward 16’s precincts 11 and 12, which vote at Florian Hall, and precinct 8, which votes at the Adams Street Library, to District 4, a Dorchester-Mattapan seat held by freshman Councillor Brian Worrell.

Advocates say the new map, in turn, unites the Vietnamese community within District 3 and Lower Mills in District 4.

In the light of the 2020 Census figures, District 2, long a South Boston bastion, had to shed population due to a boom in residents over the last 10 years, while District 3 needed to gain residents after a substantial population loss over the last decade.

Most of the proposed maps enraged Baker, who sought to keep the Neponset area and Dorchester’s Catholic parishes unified within District 3. He repeatedly berated Allston-Brighton Councillor Liz Breadon, the chair of the redistricting committee, at working sessions and hearings on the maps.

Ahead of the Nov. 2 Council vote on a final map, Baker, wearing a Celtic cross pin on his lapel, again took aim at Breadon. He said he had spoken to a Catholic priest earlier that morning, and the priest said that the city’s clergy are “all talking about this process right here, they’re viewing this exercise as an all-out assault on Catholic life in Boston. And it’s not lost on them that the person leading the charge on this is a Protestant from Fermanagh [a county in Northern Ireland].”

After a brief recess, Council President Ed Flynn, who represents District 2, said Baker had broken Council rules with the verbal attack. The Dorchester councillor attempted to apologize while saying that his district’s Catholic neighborhoods are “under attack.”

For her part, Breadon said she was raised Protestant in Northern Ireland and had been repulsed by the discrimination that Catholics faced there. She was ten years old when the sectarian strife known as “the Troubles” erupted in 1969, she noted, and in 1995 immigrated to the US, where she later married a “nice Irish Catholic girl.”

She added: “It is an insult to me to have a colleague on this City Council insinuate I am discriminating against Catholics. That is not what’s happening here. I’m standing up for the rights of minority communities — Hispanic, Asian and Black — to have equal access to voting, and to elect the candidate of their choice.”

Her remarks from the floor drew applause and councillors moved on to the matter at hand, with a majority voting to turn back amendments and pressing on to vote on the final map, which carried by a veto-proof margin: Councillors Ricardo Arroyo, Kenzie Bok, Gabriela Coletta, Tania Fernandes Anderson, Kendra Lara, Ruthzee Louijeune, and Julia Mejia joined Breadon and Worrell in voting “yes.” The “no” votes joining Baker and Flynn were at-large Councillors Michael Flaherty of South Boston and Erin Murphy of Dorchester.

The next day, when asked for comment about Baker’s remarks, a spokesman for the archdiocese of Boston called the redistricting debate “complicated” and suggested more time for deliberations over redistricting would be useful. “That said, we do not believe the process is an assault on Catholic life,” said the spokesman, Terry Donilon.

Worrell, the District 4 councillor and vice chair of the redistricting committee, said he voted for the map because Boston, a majority-minority city, must increase the opportunity for communities of color to elect candidates of their choice, which in turn could lead to more candidates of color running for City Council, He said he backed the map because “it was a vote for the realization of that opportunity, to be a possibility in the near future.”

Worrell had raised questions about an earlier version of the map, expressing concerns that pulling in high-voting white precincts in Neponset would dilute Black votes in District 4. But he was assuaged by tweaks to the map, such as amendments uniting Lower Mills and allowing him to keep parts of Codman Square. “Based on the numbers, as a district councillor, we preserved a historically Black district, which was important to me,” he said.

Court battles over the new map are still likely, though its supporters believe it can survive a legal challenge. Some South Boston and Dorchester civic groups had pressed for a delay and called for more public hearings while claiming councillors violated the Open Meeting Law at various gatherings held without sufficient public notice.

State Rep. Dan Hunt, who chairs the Ward 16 Democratic Committee, said his group plans to explore all legal options. Hunt said various maps sought to dilute the voting power of Ward 16 in a politically motivated move against the area and Councillor Baker.

“This discussion highlights people’s lack of understanding of the neighborhood,” he said, adding that it’s a diverse community.