A dozen New York lawmakers — including four Democrats and a Republican congresswoman — raced to court on Tuesday to try to block Mayor Eric Adams from opening an emergency shelter for as many as 2,000 migrants at Floyd Bennett Field in Brooklyn.

In a suit filed in State Supreme Court on Staten Island, the lawmakers accused Mr. Adams and Gov. Kathy Hochul of skirting state and federal law meant to protect the national parkland when they reached an agreement last week to lease it from the Biden administration. They asked the court for an immediate injunction, and said they were preparing another, federal suit.

“Clearly, the defendant governor and defendant mayor are seeking to establish this colony of migrants on protected federal lands, without having the light of day expose the illegal and improper aspects of their plans,” the plaintiffs wrote.

The lawsuit opens a new front in an escalating political battle over how New York should handle the crush of migrants arriving from the southwestern border. More than 110,000 asylum seekers have entered the city over the last year, straining its existing network of homeless shelters and its finances.

Mr. Adams and Ms. Hochul, both Democrats, have demanded more help from the Biden administration to try to stem the flow and move migrants out of shelters and into jobs more quickly. But because of a decades-old mandate to house the homeless, they say they have little option but to open a network of emergency shelters across the city.

Republicans have furiously objected. Joann Ariola, a Republican city councilwoman from Queens who was one of the driving forces behind Tuesday’s suit, recently called on fellow Republicans to “fully wage war” on Ms. Hochul and President Biden over their immigration policies. A growing number of Democrats have joined them in protest, albeit substituting concerns about the shelters’ effects on local services, for the more sweeping condemnations of the Republicans.

Responding on Tuesday, Mr. Adams said that the lawmakers had the right to sue, but he argued there were few better sites than Floyd Bennett Field, situated on the Jamaica Bay in southeast Brooklyn, “away from homes,” communities and school. The city finalized a lease on the site on Friday, after months of negotiations with the Biden administration.

“We’re trying to be as the least intrusive as possible to everyday New Yorkers; at the same time be as humane as possible, because we have to show that level of humanitarian aspect of this city,” Mr. Adams told reporters at an event in Manhattan.

He added: “If they don’t want it there, then they can’t get upset when it goes inside their neighborhood and block.”

Avi Small, a spokesman for Ms. Hochul, declined to comment on pending litigation.

The lawsuit portrays the site in starkly different terms, citing concerns about the risk of flooding, environmental degradation and potential impacts on nearby hospitals and emergency responders.

It was brought by a mix of City Council members, state legislators, local residents and one Republican congresswoman, Representative Nicole Malliotakis, who represents Staten Island and parts of Brooklyn. Among the Democrats were City Council members Robert Holden of Queens and Kalman Yeger of Brooklyn, as well as Assembly members Jaime R. Williams of Brooklyn and Stacey Pheffer Amato of Queens.

“It is without a doubt unacceptable, inhumane and cruel to construct a shelter and house migrants in a known flood zone like Floyd Bennett Field,” Ms. Pheffer Amato said in a statement. She said the site “lacks basic infrastructure” and would strain resources in her district.

Though the site is in Brooklyn, the suit was filed in the same Staten Island court where a judge granted a temporary restraining order in August blocking the city from housing migrants at a former school, St. John Villa Academy. The decision was later overturned.

Ms. Malliotakis opposes that shelter as well and has introduced legislation in Washington to prohibit using federal funds to create shelters on United States military bases or federal parkland, including Floyd Bennett Field and Staten Island’s Fort Wadsworth.