The most common problems uncovered by FDA inspections of 67 facilities included inadequate restroom sanitation, litter piles and indoor condensation posing a risk of food contamination by microorganisms. Inspectors also found buildings vulnerable to rodent infestation and workers with uncovered hair and poor hygiene.

Twenty serious outbreaks of E. coli have been traced to fresh lettuce or spinach since 1995. One of the most troublesome was a 2006 outbreak in bagged spinach processed by California-based Natural Selection Foods that sickened more than 200 people and was linked to three deaths.

The FDA acknowledged gaps in its food safety efforts after that episode. But the report by the House Oversight and Government Reform Committee says the problems were worse: It showed that spinach facilities were inspected about once every 2.4 years despite federal guidelines that say most should have been visited at least annually.

The FDA did not refer any of the problem facilities to its internal enforcement authorities, nor did the agency send warning letters or seek injunctions. It did refer one inspection to state authorities, the report said.

"The inspection reports . . . raise serious questions about the ability of FDA to protect the safety of fresh spinach and other fresh produce," committee investigators wrote. "It appears that FDA is inspecting high-risk facilities infrequently, failing to take vigorous enforcement action when it does inspect and identify violations, and not even inspecting the most probable sources of many outbreaks."

FDA spokeswoman Kimberly Rawlings said the agency is seeking legislative authority to implement a food protection plan that would target some produce and other high-risk foods that have been tied to serious illnesses. "Despite recent concerns, the food supply in the U.S. continues to be one of the safest in the world and this includes fresh produce," Rawlings wrote in an e-mail.

Authorities tied the 2006 outbreak to cattle or feral pig feces found in the fields of spinach grower Mission Organics. But the House report revealed that FDA inspections found repeated problems at several facilities operated by Natural Selection Foods years before the outbreak.

"FDA at no time required the firm to correct these conditions at any of its facilities, even after laboratory tests indicated the presence of microbial contamination at the exact site later implicated in the 2006 outbreak," the report's authors wrote.

Samantha Cabaluna, a spokeswoman for Natural Selection Foods, said the company has cooperated with federal and state authorities. She said parts of the committee's report are inaccurate, including a passage that alleged a July 2001 inspection found listeria bacteria in a Natural Selection Foods facility that was later tied to the 2006 E. coli outbreak. The company was not operating at that facility in 2001, she said.

"We continually search for new ways to improve food safety and note all observations provided by FDA inspectors during their audits," Cabaluna said in a statement. "Any corrective actions are immediately addressed."