The Internal Revenue Service rehired four ex-employees in recent years who left the agency amid serious conduct and performance problems, placing each of them in the same positions they had before.

The employees were among hundreds that the IRS hired for a second time despite past troubles ranging from off-duty misconduct to accessing taxpayer records without authorization.

A review by the Treasury Inspector General for Tax Administration found that the IRS overlooked past performance or conduct problems for 323 ex-staffers whom the agency rehired between January 2010 and July 2013.

(AP/Susan Walsh)

Among the four workers who returned to their previous positions, two were “failing critical job elements at the time they had separated from their prior employment with the IRS,” according to a report on the audit, released Thursday.

The review raises questions about whether federal hiring standards are strict enough. Twenty percent of the 50 randomly selected rehires with prior problems at the IRS were involved in new conduct and performance issues after they returned to the agency, according to the report.

TIGTA determined that the IRS followed federal hiring guidelines, which require checking for prior criminal activity or use of illegal drugs. But IRS officials told auditors that they barely consider prior conduct and performance issues while determining which applicants are best qualified for a job.

Roughly 10 percent of the 73,000 employees that the IRS hired between October 2009 and September 2013 previously worked at the agency. TIGTA said that “most rehired employees do not have performance or conduct issues associated with prior IRS employment.”

The IRS said in a response letter to TIGTA that management believes the current process is adequate for mitigating any risks for U.S. taxpayers. But the agency agreed to all of the inspector general’s recommendations, which called for the agency to consult with its legal department and the federal Office of Personnel Management on how to “fully consider prior conduct and performance issues.”

Senate Finance Committee Chairman Orrin Hatch (R-Utah) has promised to work with the IRS on hiring reforms. “IRS employees must be held to high standards to ensure that taxpayers are protected, and there is no reason to hire employees who have already failed to uphold those expectations,” he said Thursday.

The IRS said in a statement on Thursday that it is “committed to providing the best possible service to American taxpayers and is working to ensure it fully considers prior conduct and performance issues before the final job offer is issued to all new hires.”

Correction: An earlier version of this story included an incorrect figure for the percentage of IRS hires who were previously employed by the agency. The number has been corrected to show that about 10 percent of hires between October 2009 and September 2013 were rehires.