WASHINGTON (CBS DC) — A House hearing on the IRS targeting of conservative groups erupted into an argument between Rep. Elijah Cummings and House Oversight Committee Chairman Darrell Issa just moments after former IRS official Lois Lerner invoked her Fifth Amendment right not to testify in regards to her role in the tax scrutiny scandal.

The spat began as Rep. Issa, R-Calif., stood up to adjourn the hearing, but Rep. Cummings requested to ask a “procedural question.” While making a statement, Issa asked Cummings to yield when the Maryland Democrat became incensed at the California Republican.

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“Mr. Chairman, you cannot run a committee like this,” Cummings appealed.

“If you will sit down and allow me to ask a question,” Cummings insisted. “I am a member of a Congress of the United States of America.”

“I am tired of this,” Cummings continued, as Issa signaled to have his microphone cut off. “You cannot just have a one-sided investigation. There is absolutely something wrong with that, and it is absolutely un-American.”

“We had a hearing. It was adjourned,” Issa responded. “I gave you an opportunity to ask your questions. You had no questions.”

“I do have questions,” Cummings replied, as Issa walked out of the hearing. “Chairman, what are you hiding?”

The argument between Cummings and Issa broke out moments after IRS official Lois Lerner invoked her Fifth Amendment right not to testify about her role in singling out conservative groups for excessive tax scrutiny. Issa and Lerner’s attorneys have continued to debate whether she is still protected from testifying after giving a statement during the previous hearing.

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“On the advice of my counsel, I respectfully exercise my Fifth Amendment right and decline to answer that question,” Lerner said in response to multiple questions.

However, emails obtained by Fox News revealed that an attorney for Lerner negotiated whether or not she would testify.

After the outburst and abrupt end to the hearing, Issa told reporters that Cummings had “slandered him,” and accused him of seeking a “convenient truth” rather than following the investigative process.

“He was talking into a mic in an adjourned meeting,” Issa told reporters. “The fact is Mr. Cummings came to make a point of his objections to the process we have been going through. He was actually slandering me at the moment that the mics did go off by claiming that this had not been a real investigation.”

“Just because Mr. Cummings would like to have a more convenient truth, doesn’t give him the right to make a speech,” Issa added.

In February, a previous hearing on the same IRS scandal veered off topic when a conservative group personally accused Cummings of harassment.

President of True the Vote, Catherine Engelbrecht, stated that Cummings, “sent letters to True the Vote, demanding much of the same information the IRS had requested” after she filed for nonprofit status and then “would appear on cable news and publicly defame me and my organization,” Politico reports.

Democrats complained that it was absurd for Republicans to give the group a platform to attack a member of the committee as some Republicans attempted to change the subject back to the IRS scandal itself.

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