EPA Assistant Inspector General Patrick Sullivan testifies before the House Oversight and Government Reform Committee on Wednesday. (Alex Wong/Getty Images)

A federal investigator Wednesday accused an obscure department within the Environmental Protection Agency of acting as a “rogue law enforcement organization,” saying the Office of Homeland Security has investigated matters outside its jurisdiction and blocked independent oversight efforts.

The small department, established during the George W. Bush administration to serve as a liaison with the FBI and other intelligence agencies, has no statutory law enforcement or investigative authority.

But EPA Assistant Inspector General Patrick Sullivan testified before the House Oversight and Government Reform Committee that the 10-person agency, which comes under the office of EPA Administrator Gina McCarthy, has delved into national security and employee misconduct issues.

Sullivan also said the agency has refused to share information with his office about external threats, computer security and worker wrongdoing, citing national security concerns.

“I have zero visibility on what the Office of Homeland Security is doing,” he said. “That is the problem.”

EPA Deputy Administrator Bob Perciasepe testified that the agency works “cooperatively to provide information to the inspector general to ensure their important work is achieved.” He said McCarthy plans to meet next week with the FBI and the inspector general’s office to help clarify the Office of Homeland Security’s roles and responsibilities.

The committee’s top Democrat, Rep. Elijah E. Cummings (Md.), expressed frustration that the dispute was not already resolved. “It’s a damn shame we had to call a hearing for you all to communicate,” he said.

The interagency squabbling came to light last year when Congress began investigating former EPA deputy assistant administrator John Beale, who pleaded guilty in September to defrauding the EPA of about $900,000. He filed false time and expense reports while claiming to do undercover work for the CIA.

Sullivan said the Office of Homeland Security conducted an investigation of Beale’s conduct before his own team could review the matter. “The OHS actions, which included several interviews of Mr. Beale, delayed and damaged the OIG’s subsequent investigation,” he said.

The dispute between the two EPA offices casts further doubt on the Obama administration’s ability to carry out effective oversight after a series of notable incidents.

Homeland Security Secretary Jeh Johnson last month placed former Department of Homeland Security inspector general Charles Edwards on administrative leave after a congressional investigation found he had tailored reports to the liking of top DHS political appointees.

Separately, an Office of Special Counsel investigation found that senior officials with the Commerce Department inspector general’s office had threatened subordinates with negative performance reviews if they did not sign gag agreements around the time the OSC was investigating the inspector general for possible wrongdoing.

The House subcommittee that oversees the department issued a letter last month calling on Commerce Department Inspector General Todd Zinser to fire two of his top managers over the findings. The probe found no evidence that Zinser was aware of the officials’ actions.

The Defense Department’s inspector general also faced criticism last year after deleting findings from a draft report that said former defense secretary Leon Panetta disclosed classified information about the Osama Bin Laden raid during a CIA awards speech attended by “Zero Dark Thirty” producer Mark Boal.

The final report, which the inspector general released in June 2013, did not include the details about Panetta. It said the CIA took all appropriate measures to protect sensitive details from becoming public.