For two straight weeks, New York City police officers have sharply cut back on making arrests and issuing summonses throughout the five boroughs, magnifying the growing divide between the city’s police force and its mayor, Bill de Blasio.

Officers made half as many arrests in the seven days through Sunday as in the same week a year ago. In the entire city, 347 criminal summonses were written, down from 4,077 a year ago, according to police statistics. Parking and traffic tickets also dropped by more than 90 percent.

Most precincts’ weekly tallies for criminal infractions were close to zero: In Coney Island, the precinct covering that neighborhood did not record a single parking ticket, traffic summons or ticket for a low-level crime like public urination or drinking, the statistics showed.

The drop may present a new challenge for the mayor and his police commissioner, William J. Bratton. With officers in the country’s largest police department apparently using their own discretion to largely ignore low-level offenses, Mr. Bratton finds himself, for a brief moment, confronted with the kind of reactive force that he worked to shed two decades ago in New York City.