More than half of licensed gun dealers haven’t been inspected by the Bureau of Alcohol, Tobacco, Firearms and Explosives in at least five years, allowing dealers who have violated federal firearms laws to go undetected for years, according to a new report by the U.S. Department of Justice Inspector General.

“Between fiscal years 2007 and 2012, over 58 percent of Federal Firearms Licensees (73,204 out of 125,481) had not been inspected for five years. As a result, non-compliant FFLs go undetected by ATF for many years,” the report said. (See the complete report embedded below this story.)

Even noncompliant dealers who are detected rarely get their licenses revoked. ATF rescinds a license only for severe or repeated violations, preferring warning letters and conferences. Non-compliance can range from improperly filling out forms to neglecting background checks, the report said.

When ATF does revoke a license, the process often takes up to two years, during which time the dealer is allowed to keep selling guns. Only 62 percent of the dealers who were inspected in the last five years were in compliance with ATF rules, even though allowing dealers to go un-inspected is a serious public safety issue, according to the report.

“Statistics such as the large number of firearms that are missing, lost, or stolen from FFL inventories underline the need for prompt, effective action by ATF in this area,” the  IG report said.

ATF blamed its shortcomings on insufficient resources. The agency would need more than 1 million investigator hours to inspect all dealers within five years -- more than 200,000 investigator hours more than what it has now, according to the report. Other priorities like explosives inspections also kept investigators from conducting the inspections.

ATF has a history of inadequate inspections. A 2004 report found inspections were “infrequent and of inconsistent quality.”

“Since 2004, ATF has made a series of changes to its Inspection Program that have resulted in an improved program but, because of certain weaknesses we identified, additional actions are needed for ATF to fully achieve its goal of keeping communities safe and secure,” the report said.