FRESNO, Calif. — A crucial part of the nation's rapid-response plan — the ability to trace food through the supply chain during an illness outbreak or bioterrorism attack — is seriously flawed, an independent watchdog agency found.

Federal auditors found nearly half the food manufacturers they surveyed that are supposed to register with the Food and Drug Administration failed to give the agency accurate contact information, according to a report released today by the U.S. Department of Health and Human Services inspector general's office.

Congress set up the program after the Sept. 11, 2001, attacks to keep food safe from bioterrorism and to allow quick tracebacks when contaminated food reaches consumers.

The report follows a series of high-profile food safety problems in the U.S. involving everything from disease-ridden ground beef to the largest peanut butter recall in history.

A key lawmaker called the findings "appalling."

"The weaknesses in our food safety system that are highlighted in the report are unacceptable," said U.S. Rep. Rosa DeLauro, D-Conn., who chairs the House spending panel that oversees the FDA budget. "Congress should pass comprehensive food safety legislation to give FDA the statutory authority it needs."

Companies that manufacture, process, pack or hold food that is eaten in the U.S. are required by federal law to provide their address and basic contact information to the FDA, so investigators can follow suspect foods through the supply chain.

After interviewing managers at a sample of 130 such companies, however, government investigators found 48 percent didn't give the agency accurate information. More than half were unaware companies had to register, and about one-quarter provided no emergency contact information because current rules don't require it.

FDA officials called the report "helpful" and said it confirmed a known set of problems in the nation's food tracing system, according to comments submitted by Deputy Commissioner Dr. Joshua Sharfstein.