Rep. Stephen Lynch and arts supporters are urging Boston officials to require more parkland and performing arts facilities in the Seaport District where a developer seeks to build additional office space and housing.

“While I support job creation and significant development in the area, there must be some balance for creating and preserving open space to prevent a ‘canyon effect’ from walling off access to the harbor,” wrote Lynch, a South Boston Democrat, in a letter to the Boston Planning and Development Agency.

The debate comes as the BPDA board prepares to vote on Newton-based WS Development’s request to add 1.7 million square feet of office space and 700 additional housing units on 12.5 acres of parking lots that it acquired in 2015 for $359 million. That would update the previously approved master plan for the larger 33-acre Seaport Square site in 2010 under previous owner Boston Global Investors, which developed or sold individual parcels before selling the remaining parcels to WS.

Responding to public objections and pushback from BPDA staff comments, WS in September agreed to include a 600-seat Seaport Seaport Performing Arts Center (SeaPAC) and a 150-seat community theater.

But representatives of the Boston Lyric Opera want WS to provide a larger performing space for their organization and other arts groups.

“The BLO needs a facility that will accommodate 1,500 seats and all the pit and backstage space it sorely misses now, and the city needs a venue that all nonprofit performing arts groups can access and afford,” wrote Maria Krokidas, a member of the BLO board of directors.

Ray Stata, chairman of Norwood-based Analog Devices and a BLO board member, said an arts center with 1,800 seats would satisfy a broader segment of arts organizations and boost Boston’s economic competitiveness.

“Every major city with whom Boston will compete has a viable opera company,” Stata wrote in a public comment letter to the BPDA. “It is essential that Boston close this gap in its image as a major culture center not only to sustain growth of innovative companies but also as a destination for tourists and conventions.”

WS’s proposed project change would increase office space from 1.2 million to 2.9 million square feet, and housing from 2,500 to 3,200 units.

Other residents and Seaport workers submitted letters of support. 

Jennifer Wheaton, an eight-year Seaport resident, said she was looking forward to additional development in the neighborhood.

“I attended a briefing with WS recently and was excited to hear that only 20 percent of retail is here now so that means a lot more is coming. I disagree with the public and politicians who have said this is unwelcoming,” she wrote.

WS also is offering to pay for transportation fixes in the increasingly congested Seaport, including a 10-year, $250,000 annual subsidy for a commuter ferry to North Station, $50,000 for a study of upgrading the MBTA Silver Line’s capacity, up to $100,000 in matching funds for Silver Line upgrades and $25,000 in matching funds for a study of enhanced bus service.

A BPDA vote on the proposed changes could come as soon as next week. Spokeswoman Bonnie McGilpin said the board of director’s meeting agenda will be set on Tuesday.