“The record number of unwarranted stops is widening the rift between police and the communities whose cooperation we need to fight crime,” Mr. de Blasio said in a statement. “Make no mistake — this is the result of City Hall aggressively pushing precinct commanders to use stop and frisk beyond what is necessary and effective. It’s time to bring these numbers back to earth.”

Both Ms. Quinn and Mr. de Blasio are expected to run for mayor.

Peppered with questions at a news conference on Friday, Police Commissioner Raymond W. Kelly said that critics of the street-stop tactics “never have an answer” about how to tackle the disproportionate levels of crime in certain city neighborhoods. The department, by contrast, is always looking for answers to “slow down” crime.

“I would submit that our strategies are saving lives,” Mr. Kelly said.

He added: “You look at the numbers in this city; you look at the lives that we’re saving, and I would submit to you that the majority of those lives are minorities, and most of them are young men who are being killed for senseless reasons. We are saving those lives, and, quite frankly, we’re saving them at a much greater degree and extent than other cities are.”

Last year, there were 685,724 stop-and-frisk encounters, the highest total in the 10 years the department has reported the data. The annual total has gradually increased, from a low of 97,296 in 2002, according to departmental statistics.

So far, the numbers through March translate into an average of about 2,200 stops per day. The police said that 5 percent of the stops led to arrests and 5 percent led to summonses, slightly lower figures than in the first quarter of last year.

“If the trend continues we are headed toward a projected 730,000 or more stop-and-frisks this year, and we’re looking at well over 650,000 stops of New Yorkers who are so innocent that, in an era of zero tolerance, they walk away without even a summons,” Donna Lieberman, the executive director of the civil liberties group, said. “And the lion’s share of those impacted by the out-of-control policy are black and Latino men.”

According to the police, the numbers so far this year show that 54 percent of the people stopped were black, 33 percent were Hispanic, 9 percent were white and 3 percent were Asian. Males made up 93 percent of those stopped, the same as through last March.