NEW YORK — Saying New York created its “own little Guantanamo on the Hudson” during the Republican National Convention, a lawyer yesterday filed a lawsuit seeking relief for nearly 2,000 arrested protesters and bystanders.

“All that was missing were the orange jumpsuits,” said lawyer Jonathan C. Moore yesterday at a news conference announcing the lawsuit in federal court in Manhattan. “Under the guise of terrorism and the fear of terrorism, we are all losing our rights.”

With several plaintiffs behind him, Moore said the treatment of the protesters and bystanders violated “a bedrock principle of our democracy that the police cannot simply sweep the streets because they find protest inconvenient or embarrassing.”

He accused the city of suspending the Constitution and illegally rounding up and detaining hundreds of people “in its single-minded goal to empty the streets of political protest.” The lawsuit seeks class-action status.

“Now we see why the rights of those detained in Guantanamo (Bay) are so important to the rights of all of us,” Moore said. “Because if they are allowed to do it there they will do it here, and they did. They created their own little ‘Guantanamo on the Hudson’ equipped with chain link fences and razor wire and guards armed with machine guns escorting prisoners everywhere.”

Moore was speaking specifically of an old bus depot used as a temporary detaining facility. Detainees held there appeared in court with what appeared to be oil-stained clothing and rashes, and some had coughs.

“I could identify my clients because they were the filthiest people sitting on the bench,” said attorney Martin Stolar.

Police Deputy Commissioner Paul J. Browne said in a statement that advocates for those who broke the law continue to make false allegations about conditions at the facility where prisoners were housed.

He said police installed lighting, ventilation, sanitary facilities and other amenities and banned weapons inside.

“In fact, the police commissioner surrendered his own gun before visiting the facility,” Browne said.

He said claims that conditions at the facility were hazardous were also false.

Among those rounded up in sweeps of protesters were a World Trade Center survivor, a disabled Vietnam veteran, a children’s librarian, several professors and students, and a Jesuit priest.

Moore said many of the plaintiffs suffer continuing physical and psychological injuries and that the lawsuit would seek unspecified damages on their behalf and a change to police tactics that brought about the mass arrests.

The lawsuit alleged the arrests and a system of preventive detention were designed to keep peaceful demonstrators off the streets during the height of the convention, which ran for four days beginning Aug. 30.

It said those arrested were subjected to “intolerable and cruel and inhumane conditions,” including denying them access to family and lawyers for an unreasonable amount of time.

Kate O’Brien Ahlers, a city law office spokeswoman, had no immediate comment as her office awaited a copy of the lawsuit.

The alleged victims of the city policies included a 15-year-old diabetic who was arrested as she tried to go to a movie on 34th Street and a former vice president of Morgan Stanley who was arrested as she rode her bicycle lawfully.

The lawsuit portrayed police as eager to react to any challenge to their authority with a swift arrest, snaring curious bystanders such as 55-year-old Christopher Thomas, a Canadian, along with peaceful protesters.

Thomas, a University of Victoria professor, scholar of American art history and author of a history book, The Lincoln Memorial and American Life, said he was heading to a New York Yankees game when he was arrested.

Another of those arrested, Rebecca Stoneback, 25, said her ordeal was “deeply offensive.”

“Freedom of speech is a foundation of our country,” she said. “We’re going to fight to make sure this never happens again.”

Barbara Friedman said she could not locate her 16-year-old daughter for two days. The girl’s parents had encouraged her peaceful protest as part of participating in a democracy.

“I just see all our civil liberties slipping away,” Friedman said. “It’s very, very frightening.”