Legal Seafoods, the upscale restaurant chain, will open a location in the Charles Hotel plaza in May, despite protests from members of a neighborhood preservation group.

Legal Seafoods President Roger Berkowitz says that the company, which started in Inman Square in 1950, aims to bring quality dining to a now-vacant space by the last week of May.

But a planned expansion to the site—previously occupied by the Italian restaurant Gianinno’s—into a public plaza is drawing the fire of the Harvard Square Defense Fund, a group which has lead the charge against commercialization of the Square and intrusion upon public spaces.

Fund President Jinny Nathans said that the restaurant’s expansion, which will move the walls out about six feet to increase the space inside the restaurant, constitutes a violation of the initial agreement with the builders of the Charles Hotel complex.

“The defense fund is opposed to any expansion of the buildings that are around the courtyard because that would encroach on the open space free to the public, users of the hotel and restaurant patrons,” she said.

But Berkowitz said that Legal will merely be using the “existing footprint of the building.”

Thomas Bracken, legal counsel for the defense fund, said that his group has appealed the Planning Board’s April 1 authorization of the changes.

“It depends how you define footprint. They have put awnings outside the building which extend four or five feet and they’re planning to move the walls out to the perimeter of the awning,” Bracken said.

Bracken said that the renovation is only the latest in years of attempted expansion into public space in the Square, citing a failed renovation of the Wurst House (now Abercrombie and Fitch) and other building within the Charles Hotel courtyard.

“It’s happened two or three times in the past,” Bracken said. “Before long, that whole public courtyard will be enclosed private restaurant space.”

Hugh Russell ’64, a member of the Cambridge Planning Board, defended the expansion.

“If someone nibbles away some of the courtyard every 10 years, it’s not that big of a problem,” he said.

Construction is already underway, Russell said, and he is unaware of any reasons why the restaurant will not open on time.

“If an appeal has been filed, I’m not aware of it; nothing has come to me officially,” Russell said.

In addition to opposing encroachment upon the public space, the Harvard Square Defense Fund has fought vehemently against the proliferation of restaurant and apparel chains in the Square.

But Berkowitz said his restaurant avoids many of the negative qualities associated with chain operations.

“We hate to refer to ourselves as a chain…. A cookie-cutter operation is the antithesis of how we operate,” Berkowitz said, adding that a Harvard Square location is entirely appropriate for his restaurant. “It’s a reconnection to our [Inman Square] roots—many of our customers there came from Harvard Square,” Berkowitz said.

—Staff writer Michael A. Mohammed can be reached at mohammed@fas.harvard.edu.