WASHINGTON—Workplace injury and illness data that the Occupational Safety and Health Administration uses to assess workplace safety may be inadequate, according to a report released last week by the Government Accountability Office.

Underreporting of injuries by employers and employees, and insufficient direct contact with workers by OSHA officials may result in inaccurate data, said the GAO, which is the nonpartisan investigative arm of Congress.

Workplace injuries and illnesses often are unrecorded by employers, according to the report. Some employers avoid reporting workplace injuries and illnesses for fear of jeopardizing workers compensation premium discounts, the report said.

In addition, some workers don't report job-related injuries because they fear being fired or don't want to let their co-workers down by losing rewards for maintaining safety.

Employment attorneys acknowledge that underreporting of workplace injuries is an issue for employers and regulators, though the reasons for underreporting vary, they say.

“Sometimes it's not clear what is reportable,” said Jeffrey I. Pasek, a Philadelphia-based defense attorney at Cozen & O'Connor P.C. “Many times employees don't report to employers because they figure they have health insurance and there isn't a need to file for workers compensation.”

Mr. Pasek added that, given the economic situation and job availability, workers are willing to forgo filing a workers comp claim because they are “trying to get as much work as they can and that they are willing to work through an injury” to stay eligible for overtime.

“There is no reason, other than employer retaliation against an employee who files a workers compensation claim, that an employee who is legitimately hurt on the job should not report it,” said Alan Genitempo, an injury and employment-related claims attorney with Nutley, N.J.-based Piro, Zinna, Cifelli, Paris & Genitempo. He noted that labor laws protect an employee from employer retaliation if they file a claim and lose their job.

The GAO report said OSHA annually audits records of a representative sample of about 250 of approximately 130,000 worksites in high-hazard industries to verify the accuracy of workplace injury and illness data. While OSHA is not required to interview workers, the GAO report said taking that step could assist evaluating the accuracy of employer records.

Accurate injury and illness records by employers help OSHA identify safety issues. A lack of data hampers OSHA's efforts to encourage and regulate workplace safety, observers say.

“OSHA has to be able to trust the data it is receiving,” said Mr. Pasek. “They want to be able to identify problems before they occur.”

Mark Maser, Princeton, N.J.-based environmental practice associate and counsel for employers on OSHA enforcement for Drinker Biddle & Reath L.L.P., said more frequent audits and interviews of workers would ensure employers properly record injuries and illnesses. In addition, OSHA should increase communication and training to help employers better understand record-keeping requirements.

While the GAO cited peer pressure, loss of safety bonus rewards or company safety ratings as reasons injuries or illnesses go unrecorded, Mr. Maser said the problem could be reduced if OSHA offered incentives for employees and employers to report injuries or an unsafe working condition.

Jordan Barab, acting assistant secretary, said OSHA is developing rewards, adding that OSHA on Oct. 1 installed a national emphasis program on record-keeping in response to several studies of underreporting and congressional interest.