Before Bruce Ratner proceeds with his $3.5 billion plan to rebuild a portion of downtown Brooklyn, he first must deal with an unanticipated obstacle: a pesky e-mailer.

In a lawsuit filed Friday in U.S. District Court in Brooklyn, lawyers for Mr. Ratner claim that someone has been sending insulting e-mails in Mr. Ratner’s name to at least one prominent Brooklyn resident. The writer of the emails is not yet known, but whoever hit the send button did so with the intent of “undermining public support” for the Atlantic Yards Development Project, the complaint states.

The proposed development off Flatbush Avenue near downtown Brooklyn includes an arena for the Nets professional basketball team and 7,300 units of housing. Detractors of the plan say the development will replace local businesses and architecture with high-rise buildings and chain stores, which they say many local residents oppose.

So far, the only public evidence of the alleged anti-Ratner e-mail campaign is a fragment of a disparaging email purportedly sent on March 3 by the developer to the president of Brooklyn Brewery, Steve Hindy. Court papers claim false e-mails also have been sent to “other business, community and political leaders in Brooklyn,” but they do not specify to whom.

“Just a friendly messag [sic] to let you know I will not be selling any Brooklyn lager at the Brooklyn Nets Stadium,” court papers quote the email as reading. “Nothing personal, but I have to make a deal with the larger suppliers – Anheuser Busch for one – in order to really do the right thing. You’re small time and always will be.”

Both Mr. Hindy and a spokesman for Forest City Ratner Companies, Loren Riegelhaupt, declined to identify the address from which the e-mail was sent. The defendants in the legal complaint are listed as “John Doe Nos. 1 through 10.”

In recent weeks, Mr. Hindy, who sells beer at the current Nets stadium in East Rutherford, N.J., has come forward as a public supporter of the proposed development. His advocacy has put him in an uncomfortable position for a local brewer: the target of a neighborhood boycott.

The coordinator for the organizing effort against Mr. Hindy, Scott Turner, said he did not know of the forged e-mail and that he was not involved. But when informed of the lawsuit he said he found the e-mail amusing and an acceptable tactic in “this war of attrition.”

“People have to do what they can if they don’t have millions of dollars to spend on public relations. I think it’s fine to get in there and get dirty like that,” he said.