After he pleaded guilty last week to federal charges of evading $82,000 in taxes, Chaim Deutsch said he had no intention of stepping down from his seat on New York’s City Council.
On Tuesday, he was forced to change his plans.
Corey Johnson, the Council speaker, said that after initially believing that Mr. Deutsch, a Brooklyn Democrat, could not be expelled automatically because of the circumstances surrounding his crime, the Council had decided that the law mandated that he be ousted immediately.
“Mr. Deutsch confessed to a crime and violated his oath of office,” Mr. Johnson said in a statement, adding that the ouster was based on a review of legal documents in the case. “He is no longer a member of the City Council.”
The move came after Mr. Deutsch, 52, admitted to deducting fraudulent business expenses tied to Chasa Management, a real estate management firm that he alone owned, and to evading taxes by submitting a fraudulent federal tax return in 2015.
In announcing the plea, Audrey Strauss, the top federal prosecutor in Manhattan, said that Mr. Deutsch had “a particular responsibility to follow the law” because of his role as an elected official.
Neither Mr. Deutsch nor his lawyer immediately responded to requests for comment. He faces up to a year in prison and a $100,000 fine when he is sentenced in July. As of late Tuesday, his Twitter bio identified him as “proudly representing the people of the 48th council district.”
After the plea deal was disclosed, Mr. Deutsch’s lawyer said that his client’s ability to perform his duties as a councilman had not been “diminished” in any way. Mr. Deutsch’s plan, his lawyer said, was to pay restitution and serve out his term, which was to end on Dec. 31.
Because the crime was not a felony and not directly related to official duties, Council officials thought Mr. Deutsch could not be summarily removed under the public officers law. But after further review, officials determined that he had violated his oath of office with his plea deal, and that he should leave office immediately.
Before the Council acted, both Mr. Johnson and Mayor Bill de Blasio had urged Mr. Deutsch to resign, saying that he had violated his constituents’ trust.
“People have to have faith in their public officials.” Mr. de Blasio said at a news conference this week. “He lied for his own advantage. He cannot continue to play a role as an elected official. It just doesn’t work.”
Mr. Johnson had stripped Mr. Deutsch, who earned a base salary of $148,500 a year, of his committee assignments and his role in dispersing discretionary funds.
The councilman, who was in his second four-year term, was prohibited by city law from seeking a third. Last year, he ran an unsuccessful campaign for Congress.
A special election will not be held to fill the vacancy, officials said, but the winner of the general election in November may be able to take office immediately rather than waiting until Jan. 1.
Mr. Deutsch is the second member of the Council to be ousted in the past year. In October, the Council voted to remove Andy King, a Bronx Democrat, after an investigation found that he had violated conflict-of -interest, harassment and discrimination rules.