An interfaith group of housing and justice advocates is calling for the use of publicly owned land in Arlington for the development of affordable and workforce housing.

The group, Virginians Organized for Interfaith Community Engagement, says that Arlington County in particular needs 1,000 to 1,500 new housing units in the next five years that are affordable to people who make less than $50,000.

“The only way to significantly reduce the cost of housing is to do it on free land,” said Kathleen O’Toole, one of the VOICE organizers.

The five-year-old group wants land owned by both the public and nonprofit organizations to be used to build housing for families whose incomes fall below the 60 percent of average median income threshold. In Arlington, that is about $63,000 for a family of four. Those households often include beginning teachers, public employees, retail store and restaurant employees as well as janitors, landscapers and construction workers.

Affordable apartments are quickly disappearing from the close-in suburbs. Arlington lost about 14,000 between 2000 and 2011; tens of thousands more were lost from nearby Alexandria, Falls Church, Prince William County and Fairfax County. Most of the local governments have programs in place that try to house the homeless and encourage developers to add affordable units to their new developments, but the demand outpaces the supply. Just Friday, the county announced two projects with 76 low-income units would get financing from federal Low Income Housing Tax Credits.

The high cost of land in the 27-square-mile Arlington County eats into the cost of developing housing. The nonprofit Arlington Partnership for Affordable Housing estimates that the cost per unit of its Arlington Mill project on county-owned land along Columbia Pike is about $55,000 lower than it would be if it were built on private land. APAH’s Nina Janopaul said the savings could be up to $100,000 in other more expensive areas in Arlington.

VOICE, which is composed of almost 50 religious and community groups, is staging an assembly to demonstrate its support for more affordable housing Sunday from 4 to 6 p.m. at Mount Olive Baptist Church, 1601 S. 13th Rd. in Arlington, near Columbia Pike.