The report says the new jails “would vary in size, based on the expected population in each borough,” and would be built as close as possible to courthouses. There would be 5,500 beds across all five borough jails under the commission’s plan, with the largest one in Manhattan and the smallest on Staten Island.

Mr. de Blasio, at the news conference, denied knowledge of the recommendations of the commission, which was made up of criminal justice and prison reform advocates as well as real estate and business leaders.

According to two people with knowledge of the discussions, the mayor was briefed on the report during a Thursday evening meeting with Mr. Lippman, the former chief judge of the state’s highest court, and Ms. Mark-Viverito, and had balked at its specifics, most notably the suggestion that jails would be placed in each borough, a proposition that was “not politically viable” for the mayor, according to one of the people.

Mr. Lippman and Ms. Mark-Viverito were to discuss the commission report on Sunday at John Jay College of Criminal Justice. Mr. Lippman did not attend Friday’s news conference.

Mr. de Blasio had said last year that closing the city’s complex on Rikers Island was a “noble idea,” but he refused to publicly back it because it could cost billions of dollars, take years, and would ignore more immediate needs on the island.

But the city’s continued low crime numbers led him, more recently, to believe the jail complex could be closed.