The BRA board today approved new plans for a $500-million, 52-story tower atop Copley Place after the mall's owner agreed to add an extra five affordable apartments - an increase housing activists, such as former state Rep. Mel King, said was far from enough.

The BRA had deferred an earlier vote after some housing-activist groups said the 71 proposed affordable apartments in the 542-unit building were not enough.

Activists say Simon Property Group should comply with its original air-rights lease with the state for the land over the turnpike exit, which called for 25% of any units to be affordable - which would have meant 135 units. Simon said it complied with that in a project on Harcourt Street on the other side of the mall, but that its current lease does not call for that.

Board member Ted Landsmark said that while he's grateful Simon will replace the "not very attractive horse" that now sits in front of the mall on Darmouth Street, he was disappointed the developer was no longer willing to meet "the ethical commitment" it made initially for 25% affordable housing because of the "economic segregation" occuring in Boston, where poor people fight market-rate housing in areas such as JP so that they're not priced out of their homes and rich people downtown don't want poor people because they're poor people.

Simon Property Group says it will also spend roughly $20 million on community improvement projects, including intersection work on Stuart Street, $1 million for fixing up Back Bay station, $1 million for public art and $500,000 for the Southwest Corridor park and Copley Square.

In addition to the residential units, the Copley tower will also house an expanded Neiman-Marcus.