Not long after Philip Banks III, the New York Police Department’s highest-ranking uniformed officer, abruptly resigned on Friday, Mayor Bill de Blasio phoned several black elected officials to convey his disappointment.

By then, Mr. Banks, who is African-American, was already telling people that he resigned because he believed the police commissioner, William J. Bratton, was trying to sideline him. Although he was scheduled to begin a new civilian job that was technically the second-highest-ranking slot on the force, Mr. Banks believed it would distance him from the day-to-day running of the department and confine him to a ceremonial function.

In his phone calls, Mr. de Blasio shared that he had long harbored big ambitions for Mr. Banks, thinking of him as someone who might someday succeed Mr. Bratton, the officials recounted.

But once Mr. Banks indicated he would resign, he was allowed to leave quickly. Mr. Bratton told reporters on Monday that he had not tried to dissuade Mr. Banks of his intent to leave. (At the same news conference, Mr. Bratton dismissed one question about Mr. Banks, saying, “The chief is gone.”)

Mr. Bratton’s comments followed an unusual news conference on Sunday, when he and the mayor made a show of unity, trying to disprove reports that City Hall — and in particular Mr. de Blasio’s wife, Chirlane McCray — was angry that Mr. Bratton had managed to drive out Mr. Banks.

Their efforts seemed to have little effect. On Monday, a number of black elected officials — many of whom consider themselves allies of the mayor — suggested that City Hall should exert greater control over the Police Department’s leadership.

“When the top black and brown people resign from the N.Y.P.D., we’re worried that the atmosphere there is not yet ripe for the change we were hoping to see,” said Councilman Jumaane D. Williams of Brooklyn, a Democrat and a vocal critic of the police’s stop-and-frisk practices under the Michael R. Bloomberg administration.

While taking care to avoid criticizing the mayor explicitly, Council members seemed to express frustration with the pace of police reform on his watch.

Several members noted that they were unhappy that the number of arrests for marijuana possession, which overwhelmingly involve black and Latino males and are often the result of unjustified stops and searches, were not declining more rapidly under the new administration.

Council members also said they were worried about an overzealous application of the “broken windows theory,” which holds that curtailing low-level offenses can help root out more serious crime.

“In month No. 11, we have not seen the changes that we believe should be happening at this time,” said Councilwoman Vanessa L. Gibson of the Bronx, a Democrat and the chairwoman of the Council’s public safety committee.

The widespread support for Mr. Banks was striking, given his ascent to chief of department under Raymond W. Kelly, Mr. Bratton’s predecessor. Some of Mr. Kelly’s policing strategies came to be criticized, especially in minority communities, and that public outrage helped to propel Mr. de Blasio into office.

Yet Mr. Banks was often the point of contact for black elected officials. Many lawmakers credited him with playing a key role in quelling potentially combustible episodes, like the 2012 police shooting of an unarmed woman who ran a series of red lights in a stolen car and crashed into a minivan, or the death in July of Eric Garner, a Staten Island man whom the police placed in a chokehold while trying to arrest him for the sale of untaxed cigarettes.

“It’s not clear to me that the administration realizes the void left by Chief Banks,” Representative Hakeem Jeffries, a Brooklyn Democrat, said. “His departure is another blow to the credibility of the Police Department, at least as it relates to communities of color.”