WASHINGTON – More than a year after the Food and Drug Administration announced it had strengthened its drug safety system, the agency still lacks a reliable way to keep track of emerging problems, congressional investigators concluded in a report to be released today.

The U.S. Government Accountability Office found that a new Drug Safety Oversight Board and other FDA initiatives “are unlikely to address all the gaps” in the agency’s system for monitoring the long-term safety of prescription drugs approved for market.

While the board may help straighten out high-profile cases, the GAO said, day-to-day oversight of safety issues is still hampered by poor information, lack of legal authority to order drug-company studies, and bickering between the powerful FDA bureau that reviews drugs for approval and a smaller safety office depicted in the report as a bureaucratic stepchild.

The safety office “serves primarily as a consultant” to the Office of New Drugs “and does not have any independent decision-making responsibility,” the report said. In some cases, it found, the new drug bureau has excluded safety officers from presenting their findings to scientific panels that the FDA relies on for advice.

With eight directors of its safety office in the last 10 years, the FDA “has not effectively overseen post-market drug safety issues, and as a result, it is unclear how [the agency] can know that important safety concerns have been addressed and resolved in a timely manner,” the report said.

It is too early to tell whether the report will provide a boost for stalled legislation to beef up the FDA’s safety office and make it an independent center within the agency. While GAO investigators outlined a long list of unresolved problems, they credited the FDA for working to make improvements. In a statement, the FDA vigorously disputed the finding that its safety office plays a secondary role.

Two key lawmakers who requested the GAO inquiry were divided in their reactions to the report.

“The GAO report shows that the drug safety system is not in crisis, but the FDA’s process may need some fine tuning,” the chairman of the Energy and Commerce Committee, which oversees the pharmaceutical industry, Rep. Joe Barton, a Republican of Texas, said.

A spokesman said Mr. Barton would wait for a National Academy of Sciences report due this summer before deciding whether to pursue legislation.

Senator Grassley, a Republican of Iowa, co-author of the FDA reform bill, said the findings by nonpartisan investigators bolstered his proposal. Mr. Grassley held widely publicized hearings into the FDA’s failure to identify the heart risks of Vioxx despite warnings from its safety office. The hearings followed an unexpected decision by manufacturer Merck to withdraw the painkiller, which had racked up blockbuster sales and profits.

“At the Vioxx hearing, some said there was a crisis at the FDA and others said everything is all right,” Mr. Grassley said. “This report provides solid evidence that everything is not all right … the FDA’s problems are systemic and cultural, not isolated or easily fixed.”