171 Tremont St.

A 12-unit luxury condominium tower that was reduced in height to comply with regulations protecting Boston Common from shadow has received final approval from city officials.

The Boston Planning and Development Agency (BPDA) approved the 155-foot-tall tower at 171 Tremont St. Thursday.

Swiss developer Maurice Dabbah originally proposed a 355-foot-tall building for the site, which currently is occupied by a 4-story office building. Neighborhood residents and the Friends of the Public Garden objected to the design, which would have required zoning variances.

Dabbah also eliminated all 21 resident parking spaces in favor of two valet drop-offs. In public filings, the developer said the Elkus Manfredi-designed building will contribute to the revitalization of Downtown Crossing.

Potential approval of General Electric’s new 399,700-square-foot headquarters in Fort Point was delayed Thursday after a coalition of activists claimed that the BPDA board of directors violated the state Open Meeting Law.

In an Oct. 20 letter to the board, the group, Make GE Pay, said the last seven items on the agenda were not visible when posted on a city hall bulletin board. The board will take up the Gensler-designed complex again at a future meeting, spokeswoman Gina Physic said.

GE, which recently moved into temporary office space on Farnsworth Street, hopes to complete construction of the new building and redevelopment of two warehouses on Necco Way in 2018.