Dozens of the worst-run nursing homes in the United States have mortgages guaranteed by a federal agency that mostly stopped inspecting such homes several years ago.

Seventy-four nursing homes with mortgages insured against default by the agency, the Department of Housing and Urban Development, are among 478 homes identified this month by two United States senators as having “serious deficiencies.”

That dozens of taxpayer-backed homes appeared on the list reflects the federal government’s spotty history of monitoring for-profit nursing homes that can use the housing agency’s backing to obtain more favorable terms from lenders. The agency’s inspector general has criticized the oversight of nursing homes that belong to the program, known as Section 232, and last month the chairman of the House Ways and Means Committee asked the agency to reinstitute the property inspections, which were largely discontinued in 2012.

The mortgage insurance program is a vital financial lifeline to the nursing home industry, but some people contend that the program must do more to ensure better business practices.