The nation is in danger of losing as much as 80 percent of the privately owned but federally subsidized housing for low-income people over the next 15 years, a special bipartisan commission warned Wednesday.

The National Low Income Housing Preservation Commission, in a report to congressional housing committees, said that if no action is taken, 523,000 of the 645,000 units of subsidized housing are likely to be lost either through mortgage default or conversion by owners to higher paying uses, leaving only 122,000 units available for low-income housing.The commission was co-chaired by Carla Hills, Secretary of Housing and Urban Development in the Ford administration and Henry Reuss, former chairman of the House Banking, Finance and Urban Affairs Committee.

In its 136-page report, the commission said the existence of the 645,000 units "represents a prior federal commitment to provide this number of units for occupancy mainly by low-income households."

"The federal government should accept primary responsibility for maintaining that commitment for at least the next 15 years," the report recommended.

It called for creating a new office of low-income housing preservation within the Department of Housing and Urban Development to work with state and local government to develop and implement preservation plans aimed at retaining specific properties as low-income housing where it is "cost-effective" to do so.

It defined "cost-effective" as actions that would maintain a unit for 15 years at no greater cost that the Office of Management and Budget's estimated 15-year cost of a housing voucher $30,000.

It predicted the cost of saving the 473,000 units from default or prepayment by the private owners and to protect the 50,000 households likely to be displaced, would cost $11.3 billion in new funding and $6.4 billion to continue subsidies already granted by the government.

It said the cost of providing housing vouchers the administration's favored program that allows voucher recipients to seek housing in the private market would cost $21 billion for the 523,000 households.