Robert Stolarik for The New York Times

A federal judge on Wednesday granted class-action status to a lawsuit challenging the New York Police Department’s stop-and-frisk tactics, saying she was disturbed by the city’s “deeply troubling apathy towards New Yorkers’ most fundamental constitutional rights.”

The decision by the judge, Shira A. Scheindlin, of Federal District Court, (see also below) provides possible legal recourse for hundreds of thousands of people who have been caught up in the department’s increasingly vigorous stop-and-frisk practice, which critics say unjustly ensnares blacks and Latinos.

Over the weekend, the police disclosed that they had made more than 200,000 such stops in the first three months of 2012, placing the Bloomberg administration on course for the largest number of annual stops in the 10 years the department has been measuring them.

In granting class-action status to the case, which was filed in January 2008 by the Center for Constitutional Rights on behalf of four plaintiffs, the judge wrote that she was giving voice to the voiceless.

“The vast majority of New Yorkers who are unlawfully stopped will never bring suit to vindicate their rights,” Judge Scheindlin wrote.

The judge said the evidence presented in the case showed that the department had a “policy of establishing performance standards and demanding increased levels of stops and frisks” that has led to an exponential growth in the number of stops.

But the judge used her strongest language in condemning the city’s position that a court-ordered injunction banning the stop-and-frisk practice would represent “judicial intrusion” and could not “guarantee that suspicionless stops would never occur or would only occur in a certain percentage of encounters.”

Judge Scheindlin said the city’s attitude was “cavalier,” and added that “suspicionless stops should never occur.”

Despite the judge’s ruling and her pointed language, the city is unlikely to change its course. Asked about the decision at a news conference at Police Headquarters, Raymond W. Kelly, the police commissioner, would say only, “It is what it is.”

Nonetheless, with the stop-and-frisk policy under attack from the judge and the presumed Democratic candidates in the 2013 mayoral race, it seems plausible that the city could contemplate some changes.

“Every page of that ruling has some troubling news for them,” said Eugene J. O’Donnell, a professor at the John Jay College of Criminal Justice. “I sense there is a tipping point on this, and I don’t think there is a single mayoral candidate who has not expressed concern on this program.”

Richard Aborn, the president of the Citizens Crime Commission of New York City, said things should never have gotten this far.

“This is precisely what happens when the city declines to have independent oversight over the department,” he said, “so you end up with oversight by litigation, which generally comes after the fact and ends up being far more costly than if an inspector general would intervene early.”

Blacks and Hispanics generally represent more than 85 percent of those stopped by the police, even though their combined population makes up a smaller share of the city’s racial composition.

Critics, including the New York Civil Liberties Union, also point out that the number of people arrested or issued summonses hovers around 10 percent of the stops — suggesting that a majority of those stopped have done nothing wrong.

In the past, Mr. Kelly has rejected the notion that officers engage in racial profiling, and he has argued that the street stops have helped reduce crime and save lives by leading to the seizure of illegal guns.

Darius Charney, a lawyer with the Center for Constitutional Rights, pointed to a part of the decision in which the judge noted that there was “indisputable evidence” that the department’s street-stop program stemmed in design and implementation from the highest levels of the agency.

“This is not just about five or six bad officers; this is about a whole department’s policies and practices,” Mr. Charney said. “Which is why the best way to proceed with this case is as a class action, because it affects hundreds of thousands of people in the city.”

Connie Pankratz, a spokeswoman for the city’s Law Department, said it was too early to discuss whether the city would appeal the ruling. “We respectfully disagree with the decision and are reviewing our legal options,” she said.

Lalit Clarkson, 30, a plaintiff in the suit, was returning to work as a teacher’s aide at a charter school in the Bronx in 2006 when two officers stopped him to search for drugs. He said it did not matter how or when the department changed its policy, just as long as change happened.

“At the end of the day,” he said, “I think many folks in our community feel there is no accountability for when their rights are violated by the police.”