The EPA was accused Wednesday of tolerating waste, fraud and "criminal conduct" in its own ranks, as a House committee hearing aired allegations of employee misconduct that have cost taxpayers hundreds of thousands of dollars.

The inspector general's office -- the official watchdog tasked with overseeing the agency -- also claims it's being blocked from doing its job by a unit within the EPA.

"I'm very concerned that vital information regarding suspected employee misconduct is being withheld from the OIG," Patrick Sullivan, assistant inspector general, testified before the House Oversight and Government Reform Committee.

"This is truly a broken agency," committee Chairman Rep. Darrell Issa, R-Calif., said, adding that the employee problems have gotten to the point of being "intolerable."

The committee revealed several startling allegations and cases shared by the inspector general's office. In one case, an employee was getting paid for one or two years after moving to a retirement home, where the employee allegedly did not work. When an investigation began, the worker was simply placed on sick leave.

More On This...

In another case, an employee with multiple-sclerosis was allowed to work at home for the last 20 years. However, for the past five years, she allegedly produced no work -- though she was paid roughly $600,000. She retired after an investigation.

In yet another case, an employee was accused of viewing pornography for two-to-six hours a day since 2010. An IG probe found the worker had 7,000 pornographic files on his EPA computer.

At the hearing, Sullivan detailed specific concerns with the agency's little-known Office of Homeland Security.

The office of about 10 employees is overseen by EPA Administrator Gina McCarthy's office, and the inspector general's office is accusing it of operating illegally as a "rogue law enforcement agency" that has impeded independent investigations into employee misconduct, computer security and external threats, including compelling employees involved in cases to sign non-disclosure agreements.

EPA Deputy Administrator Bob Perciasepe told Congress that the agency's employees work cooperatively with the inspector general and support its mission.

Perciasepe assured Congress that the EPA remains committed to ensuring that the inspector general's office successfully roots out waste, fraud and abuse across the agency. He said some of the cases aired Wednesday are "not the norm."

The inspector general, Arthur A. Elkins, Jr., was appointed to lead the office by Obama in 2010. However, it's an independent office within the agency expected to be outside of political influence.

EPA's Office of Homeland Security was set up in 2003 by an administrative order, and has no statutory authority to conduct investigations or enforce the law, according to Sullivan's testimony. Sullivan's opinion was backed up by a staffer in the Office of Compliance and Enforcement Assurance, but the agency has not issued a legal opinion on the office's role. Since July 2012, in an agreement with the FBI, it has been the primary contact on all investigations with a connection to national security.

The dispute between the inspector general's office and the Homeland Security office came to a head last year, as Republicans in Congress investigated the agency's handling of John C. Beale, a former deputy assistant administrator who pleaded guilty in federal court last fall to stealing a total of $886,186 between 2000 and April 2013, falsely claiming he was working undercover for the CIA. The Beale case was initially investigated by the Homeland Security office months before the IG's office was made aware of it.

Sullivan said Wednesday that the office's actions delayed and damaged their own probe.

Further, he claimed a "total and systematic refusal" to share information has stymied investigations. Sullivan said the office for years has blocked the inspector general's office from information by citing national security concerns and compelling employees to sign non-disclosure agreements.

Another inspector general investigator, Elisabeth Heller Drake, testified that the EPA asked the inspector general's office to halt a probe into a homeland security office employee after he allegedly assaulted her in October.

Drake testified that she attempted to interview John Martin, an intelligence adviser and special agent in EPA's Office of Homeland Security, but that he would not answer basic questions. After Drake realized that Martin left without signing a nondisclosure form, she tracked him down and found him discussing the interview with two other EPA employees.

EPA Intelligence Adviser Steven Williams then approached Drake and yelled at her, jabbing his finger near her chest, she claimed. "His veins bulged and he began to sweat profusely," she said, adding that she felt "intimidated."

Drake later filed an assault complaint.

The EPA says that claim is a mischaracterization and that McCarthy only asked that the investigation be paused until the internal dispute between the two offices was settled safely and efficiently.

Both the IG's office and the EPA's lawyers have requested a third-party investigation into that incident by the Federal Protective Service, part of the Homeland Security Department.

EPA spokeswoman Alisha Johnson told E&E Publishing in March that the EPA and the IG's office were "working together to resolve our disagreement regarding areas of responsibility within matters related to national security."

The Associated Press contributed to this report.