Residents of the Harbor Towers condominiums called for developer Donald Chiofaro to eliminate one of his two proposed skyscrapers on the Boston waterfront.

The condo trustees said the project should be scaled back to a single tower concept submitted to them by architect George Thrush, director of Northeastern University’s School of Architecture. The Thrush plan also has different ground-floor designs that would preserve more open space and improve pedestrian access to the waterfront, Harbor Towers trustees said in a statement released Tuesday.

Boston-based Chiofaro Cos. has proposed a pair of 615- and 538-foot-tall towers containing 1.3 million square feet of commercial and residential space, replacing the eight-story Harbor Garage on India Street.

The Harbor Towers trustees said more than 550 residents and owners in the two 40-story buildings have signed a petition objecting to Chiofaro Co.’s plan.

Chiofaro has stated that 1.3 million square feet is the minimum needed for a financially feasible development. The Harbor Towers trustees, citing an analysis by two unnamed real estate executives, said the 1.3-acre site could support an economically viable plan with only 725,000 square feet of development.

"They told us that being allowed to build that much would be considered a valuable business opportunity by any experienced developer," Lee Kozol, chair of the Harbor Towers Garage committee, said in a statement.

The economic analysis has been submitted to the Boston Redevelopment Authority, which is reviewing conceptual plans for the project.

For the project to go forward in its current form, the BRA would have to waive maximum height and minimum open space limits for waterfront developments.