For two decades, Rep. Jerrold Nadler has been championing construction of a freight rail tunnel between Brooklyn and New Jersey, and he has a long line of colleagues in city, state, and federal government who have lined up with him to support it.

The idea of the Cross Harbor Freight Rail Tunnel, as it’s called, is to create a tunnel under New York Harbor and use an existing above-ground rail line to carry goods into the city for delivery at Queens.

The project, proponents say, could eliminate up to 1 million truck trips a year across the Hudson River crossings and reduce the pollution that causes asthma and other respiratory problems.

Mr. Nadler, a Democrat who represents parts of Manhattan and Brooklyn, has been dogged of late, however, by fierce opposition from residents along the existing rail line, who argue that even the current train traffic through their neighborhoods is difficult to live with and that besides creating many more train trips the plan would shift a lot of the truck trips to pick-up points in Queens.

In December, a 60-foot-by-20-foot billboard was erected over the Long Island Expressway, near the proposed depot where trucks would load up their merchandise, bearing Mr. Nadler’s name and phone number. More recently, Mr. Nadler has been ensnared in an Op-Ed battle with City Council Member Simcha Felder in the Jewish Press.

Mr. Felder, a Democrat who represents neighborhoods the rail line would pass through in Brooklyn, says additional freight trains would barrel past newly built schools and homes, destroying the quality of life for hundreds of residents by ramping up noise and pollution.

“I don’t have a problem saying ‘Not in My Backyard,'” Mr. Felder said yesterday. “It’s not just my backyard. You’re talking about hundreds of people’s backyards here.”

In early December, Mr. Felder, along with Council Member Dennis Gallagher, a Republican of Queens, delivered anti-tunnel petitions with 10,000 signatures to the city’s Economic Development Corp., which is studying the project.

Though the agency did not return calls for comment yesterday, at the time a spokesman, Michael Sherman, was quoted as saying that the concerns were being taken seriously. A draft environmental impact study sponsored by the agency, however, concluded that the tunnel would produce economic and environmental benefits.

The issue could emerge as an important one in this year’s mayoral race. In April 2003, Mayor Bloomberg said he supported the tunnel, but he has not said much since. Although the Economic Development Corp. produced a favorable draft study last year, it was under Mayor Giuliani, a proponent of the project, that the agency first took on the issue.

Mr. Bloomberg is scheduled to appear tomorrow night at the Middle Village Juniper Park Civic Association in Queens and will probably have no choice but to talk about it. Mr. Felder said he expects the mayor to come out against the project, given the recent community opposition, which is focused at several potential swing districts for the fall election.

The mayor’s office referred questions about the project yesterday to the Economic Development Corporation.

The three Democratic mayoral contenders who currently hold public office are all on the record supporting the tunnel: the speaker of the City Council, Gifford Miller, of Manhattan; Rep. Anthony Weiner, who represents a Brooklyn-Queens district; and the borough president of Manhattan, C. Virginia Fields.

The tunnel project is expected to range in cost from $4.8 billion to $7.4 billion, depending on whether a double or single rail is built.

Mr. Nadler, who secured $22 million in federal money to have a study of the project conducted, said the George Washington Bridge needs to be relieved of the huge amount of truck traffic it handles and the city needs a backup route for freight in the event of a catastrophic accident or terrorist attack.

He acknowledges that if the tunnel is built there would be more trucks at the loading points in Queens, but he says that the number is not nearly as high as some in the community suggest and that there are ways to address those problems, such as building a ramp directly from the depot to the highway so that trucks don’t go through city streets.

Further, Mr. Nadler says, even if the New Jersey-Brooklyn tunnel is never built, more freight will be coming into the city by water and loaded onto trains at the Maspeth depot because road congestion is getting so bad.

“In most American cities, 40% of all freight, everything from grapefruit to Xerox machines, comes in by rail,” the congressman said yesterday. In New York City and the surrounding area, that proportion is 2%.

The Economic Development Corp. has said 30,000 trucks a day cross the George Washington and Verrazzano-Narrows bridges into the city. The agency estimates that incoming freight will jump by 50% over the next 20 years.

Mr. Felder, however, said: “Anyone can get the results they want from a study.” The large trucks would simply be replaced with smaller trucks picking up goods in Maspeth, he said, where surrounding communities would be choked with traffic from the very diesel-spewing vehicles Mr. Nadler wants to see go.

“How is the rice going to be delivered to Avenue J in Brooklyn and how is the applesauce going to get to the babies in Queens?” Mr. Felder said. “The train is not going to stop along the way. It’s going to stop at the end and get picked up by a truck. It may reduce the number of large trucks, but there are still going to be small trucks making these deliveries.”

Mr. Felder is not alone among elected officials in questioning the project.

“The plan may be good for the city as a whole, but I have some real concerns about impact on the quality of life, especially in Queens,” Council Member Eric Gioia, Democrat of Queens, said. “These are questions that need to answered.”

“This idea has great potential and the possibility of removing a large number of truck makes it appealing, but it’s impossible to support it until the administration has answered the community’s questions,” Council Member Bill de Blasio, a Democrat who represents parts of Brooklyn, including Boro Park, said.

Mr. Nadler expected to be in Washington today when the Transportation Committee votes on a bill that includes the tunnel project.