An effort to indefinitely extend a Baltimore law that requires developers to build affordable housing units along with market-rate homes received the backing of a key City Council committee today, although it's unclear how the measure will fare when the full council takes it up Monday.

The 2007 law, which was championed by Council President Bernard C. "Jack" Young, requires developers to set aside a certain percentage of homes, condominiums or apartments to be sold or rented at lower rates for large developments that receive significant public subsidies or meet other criteria.

Only one development project, Union Mill in Hampden, has triggered the terms of the law, resulting in the construction of 10 affordable units. Seawall Development, the builders of that project, also tapped into the city's affordable housing fund to construct 20 units in other projects.

Affordable housing advocates say the law was watered down in 2007 when the council -- following recommendations of a panel of developers -- passed nearly 100 amendments, including some which slowed the implementation of the law.

Mel Freeman, the executive director of the Citizens' Planning and Housing Association a major proponent of the measure, is lobbying council members to extend the law indefinitely. He hopes to then amend the law to make it apply to more projects.

The bill was "beat up pretty bad in 2007," he said. "Getting the sunset removed gives us time to go back to the table and work on those amendments."

The law was intended to open opportunities for low-income residents to live in neighborhoods where they have access to quality schools, grocery stores, parks and other amenities, he said.

"The issue is quality affordable housing," said Tammy Mayer, community engagement director for Citizens Planning and Housing Association. "If you segregate all your affordable housing in one area, you wind up with ghettos."

Councilwoman Mary Pat Clarke, who voted to repeal a provision that would have repealed the law next year, said the law "deserves to have a wide horizon of time" to demonstrate its efficacy.

Council Vice President Edward Reisinger, who chairs the Transportation and Land Use committee, voted in favor of the bill, but said he planned to introduce an amendment to it on Monday.

Mayor Stephanie Rawlings-Blake is pushing for the bill to sunset in 2020, a spokesman said.

Rawlings-Blake "supports an extension of law to July 2020 which would give more time for the housing market to recover and give the City a better understanding the of effectiveness of the ordinance in providing affordable housing opportunities," spokesman Ryan O'Doherty said in an email.

The city's planning and housing departments recommended that the law be extended for a finite period. The finance department wrote in a letter to council members that the law is "neither cost-effective nor sustainable," noting that it had yielded 20 housing units at a cost of approximately $87,500 per unit.

Four members of the council's Land Use and Transportation Committee voted to support the indefinite extension: Reisinger, Clarke, Bill Henry, Sharon Green Middleton and Warren Branch. Two members, Belinda Conaway and James B. Kraft, were not present for the vote.