The U.S. Department of Agriculture did not evaluate the accuracy of worker safety data it used to make its case for a new hog inspection system that allows plants to run processing lines at unlimited speeds, the Office of Inspector General has concluded.

The report, which was released Wednesday, also found that USDA was not transparent about the raw data it used in its worker safety analysis, making it impossible for outside experts to evaluate the agency’s conclusions.

The new system, which was finalized in October, shifts many food-safety tasks from federal inspectors to pork industry employees and reduces the number of USDA inspectors on slaughter lines in some plants by 40 percent, records show.

Prompted by the inspector general report, a nonprofit group opposed to the new system said it will ask a judge to set aside the rule that created it.

When USDA proposed the new rule, which is voluntary for plants, it concluded injury rates for workers would likely be lower in the plants using the new system.

Worker safety advocates challenged these conclusions. They said workers would be working at a faster pace as they slaughtered hogs and then performed the intricate and repetitive work of cutting them into chops, hams and loins.

Illness rates for people who work in meatpacking plants — including carpal tunnel syndrome and tendinitis — are 16 times higher than the average for all other industries, according to the U.S. Bureau of Labor Statistics.

The inspector general said that during the public comment period, USDA provided an analysis on worker safety based on Occupational Safety and Health Administration records it did not provide to the public. And the inspector general “determined that [USDA] did not compare the OSHA data to any corroborating evidence to verify the reliability of these data used.”

USDA also “neither ensured that the data in the proposed rule were presented in an accurate manner nor disclosed all known limitations of the data,” the 36-page report said.

USDA’s Food Safety and Inspection Service (FSIS) said in an email that the inspector general misapplied information to a preliminary analysis that was not made in support of its proposal. “Further, the OIG findings place an exaggerated emphasis on minor errors made in the presentation of the analysis – errors already corrected.”

Public Citizen, a nonprofit advocacy group, filed a lawsuit last year seeking to block the new program from moving forward, saying USDA’s “refusal to consider the harms its actions will have on workers reflects arbitrary and capricious decision making and thus violates” a federal law governing the rulemaking process.

On Wednesday, attorney Adam R. Pulver said his group will argue the flaws identified in the inspector general’s report require USDA to start its rulemaking for hog slaughter over again.

Debbie Berkowitz, a worker-safety expert with the National Employment Law Project, and a Texas State University researcher filed a Freedom of Information Act request for the undisclosed data in 2018. But it wasn’t released by USDA until after the 60-day public comment period on the proposal had ended.

Two Texas State University researchers reviewed USDA’s data and analysis and concluded “it is impossible” for the department to “draw any statistically valid conclusion about worker injury rate differences” from it.

“This is an unsparing rebuke of the USDA,” Berkowitz said.

In response to the university researchers’ findings, Sen. Richard J. Durbin (Ill.), the second-ranking Senate Democrat, and more than a dozen other Democrats last year sought the inspector general’s probe.

In a statement, Durbin said Wednesday: “Today’s report confirms my concerns: that FSIS was not forthcoming about its worker safety analysis and used questionable data in developing a dangerous change to meat plant operations. Sacrificing worker safety for industry profits is unacceptable and FSIS has earned the doubt and scrutiny it received through this report.”

When USDA proposed the new system, it said it expected 40 of 612 hog plants would use the new system. Collectively, agriculture officials say, these plants will account for 90 percent of the pork produced in the United States. USDA said Wednesday that seven plants have converted to the new inspection system.