A federal judge in Manhattan criticized police officials yesterday for the way demonstrators against the war in Iraq were interrogated earlier this year, and he made clear that civil liberties lawyers could seek to hold the city in contempt of court in the future if the police violate people's rights.

The judge, Charles S. Haight Jr. of Federal District Court, who recently eased court-ordered rules on police surveillance of political groups, made his comments after hearing evidence that the police had asked the protesters their views on the war, whether they hated President Bush, if they had traveled to Africa or the Middle East, and what might be different if Al Gore were president.

"These recent events reveal an N.Y.P.D. in some need of discipline," Judge Haight wrote, citing what he called a "display of operational ignorance on the part of the N.Y.P.D.'s highest officials."

In his ruling, Judge Haight cited comments in the news media by the police commissioner, Raymond W. Kelly, that he and his deputy commissioner for intelligence, David Cohen, were unaware that the police were using what they called a "debriefing form" in the questioning.

"The two commissioners should have known," the judge wrote.

In February, Judge Haight agreed to modify a longstanding court order that had restricted the Police Department's ability to conduct surveillance of political groups. Police officials had said they needed greater flexibility in investigating terrorism, and the judge agreed to ease the rules, citing "fundamental changes in the threats to public security."

The original rules were known as the Handschu agreement, named for the first listed plaintiff in a 1971 lawsuit over harassment of political advocacy groups by the Police Department's so-called Red Squad.

Yesterday, Judge Haight did not impose new restrictions on the police in the wake of the interrogations, which first came to light after the New York Civil Liberties Union received complaints from protesters. Nor did the judge decide the issue of whether the interrogations violated the protesters' constitutional rights.

But he said he would formally incorporate the recently eased rules into a judicial decree, to make clear that lawyers could return to court and seek to hold the city in contempt if they believed that a violation of the rules also violated an individual's constitutional rights.

"This approach gives the plaintiff class an increased protection warranted by recent events without unfairly burdening the N.Y.P.D.," the judge said. The ruling, he added, should not "unduly trouble the N.Y.P.D., which I will assume is not engaged in thinking up ways to violate the Constitution."

Jethro M. Eisenstein, a lawyer for the plaintiffs, said that the judge made clear "that these rules are not window dressing."

"They're actual rules, they limit what the Police Department can do, and if the Police Department goes beyond them, they face the risk of being held in contempt," he said, adding that contempt power can result in swift fines and imprisonment. "You don't have to start a lawsuit and reinvent the wheel."

Commissioner Kelly, who said he had not read the entire ruling, noted that the judge had not altered the recent modifications for which the Police Department had petitioned, "so it allows us to go forward."

"I think significant for us, the modifications that were made stay in place," the commissioner said.

Gail Donoghue, special assistant to the city corporation counsel, said, "The city feels that the decision has not adversely impacted on the N.Y.P.D.'s ability to remain proactive in the investigation and prevention of terrorism."