The administration was accused yesterday of seriously undermining federal meat and poultry health protections by relaxing health standards and overworking inspectors because hundreds of positions have been left unfilled.

The charges were leveled in a report by Ralph Nader's Center for the Study of Responsive Law, which called for immediate congressional hearings on what Nader termed "deplorable" policy changes and suppression of inspection reports by the Agriculture Department.

The report, prepared by Nader aide Kathleen Hughes, said that the increased workload, in combination with relaxed standards, had demoralized Food Safety and Inspection Service workers and opened the way for more contaminated meat to reach consumers.

"The administration's policies make it more difficult for inspectors to detect diseased and adulterated meat, and make it easier for packers who operate under unhealthy conditions to hide from public view," Hughes wrote. "Most of the changes are administrative. They were never debated in Congress."

Nader and other consumer advocates appeared at a news conference with a retired USDA meat grader, John Coplin of Darien, Ill. Coplin announced plans to file a complaint with the Special Counsel of the Merit Systems Protection Board, charging USDA with violating its meat and poultry oversight duties.

The Nader report was based on a review of federal records and on dozens of interviews with federal inspectors. Thomas Devine of the Institute for Policy Studies said Coplin's charges of corruption were supported by affidavits from inspectors and graders.

Their charges were "endorsed and verified" by Delmer Jones of Birmingham, Ala., chairman of the National Joint Council of Food Inspection Locals, which represents about 6,000 federal employes. Jones said "the integrity of the process has been compromised" by administrative changes that have speeded up inspections and reduced enforcement.

USDA spokesman John McClung said the department regarded the report as "a very superficial, undisciplined treatment . . . . Miss Hughes didn't understand what she was dealing with in some instances." As an example, he said, the report described Coplin as a former inspector, when he was a meat grader.

McClung contended the inspectors' endorsement of the Nader report stemmed more from concerns about threats to their jobs, posed by budget cuts and new inspection systems, than it did from health and safety concerns.

The American Meat Institute, which the report said was unduly influencing USDA policy, responded that "Americans enjoy the safest and most wholesome meat in the world." AMI said it would be "senseless and irresponsible" to participate in "emasculation of the very system that serves to give confidence to consumers."

The report noted that Richard E. Lyng was president of AMI before he became deputy secretary of agriculture, and C.W. McMillan, the assistant secretary who is responsible for food safety, previously was a lobbyist for the National Cattlemen's Association.