Both sides of City Hall are tackling shortcomings in the city’s housing stock,with Mayor Bloomberg yesterday detailing plans to build more “affordable” units as the City Council speaker, Christine Quinn, proposed a bill targeting dilapidated apartment buildings and their landlords.

Seeking to make good on a major campaign pledge, the mayor announced the first developments in what he said was the largest municipal affordable housing plan in the nation’s history. The 10-year, $7.5 billion project aims to build or preserve 165,000 units that could accommodate 500,000 low- and middle-income New Yorkers.

Appearing with housing officials at Lenox Gardens in Harlem, the mayor said the city had awarded contracts to 22 developers to build more than 1,100 units for rent and sale in Manhattan, Brooklyn, and the Bronx. Mr. Bloomberg said 84% of the units would qualify as “affordable.” They are slated for completion in 2009.

The mayor also announced the development of 435 units intended for middle-class families in West Chelsea and Hudson Yards. The units will be built on city-owned land and would also be occupied by 2009, Mr. Bloomberg’s last year in office.

As he did during his run for re-election, Mr. Bloomberg cast the need for increased housing as a case of the city being a victim of its own success. “We like the idea that lots of people like to live here,” he said.

While the mayor touted the progress of his housing plan in Harlem, Ms. Quinn eyed flaws in the city’s transitional housing system for formerly homeless families. The speaker proposed a bill aimed at preventing city agencies from placing New York’s neediest in buildings with significant code violations.

Appearing at City Hall with other council members and housing advocates, Ms. Quinn cited a 2004 council study that found that New Yorkers with HIV/AIDS who were on public assistance were often placed in apartments that lacked essentials like heat, hot water, and electricity. The bill would prohibit the city from referring a formerly homeless family to buildings that do not meet certain health and safety standards.

In many cases, the apartments are subsidized with taxpayer dollars. If passed, the bill could force negligent landlords to improve conditions or face a hit to their wallets with the loss of government payments, the speaker said.

“Since these landlords in many cases make a great deal of money off of these placements,” Ms. Quinn said, “we believe this bill will be a carrot and stick that will cause many of these conditions to change significantly and greatly expand the universe of quality housing that exists for New Yorkers in need.”

Ms. Quinn, a Democrat and longtime housing advocate, has maintained positive relations with Mayor Bloomberg early in her tenure, and she notably avoided criticizing him yesterday. She said the problem in housing placement “far predated the Bloomberg administration.” She directed the majority of criticism at the landlords who allowed poor conditions to persist.

Asked about the speaker’s proposal, Mr. Bloomberg did not say whether he supported it but praised Ms. Quinn for “trying to tackle a lot of issues head-on.”