It appears Ms. Lerner's promise to co-operate with the congressional committee was hollow as she invoked the 5th when she said she would co-operate.

A House hearing on the IRS targeting scandal rapidly broke down into a heated and deeply personal argument between a top Democrat and Republican, moments after former IRS official Lois Lerner once again invoked her Fifth Amendment right not to testify.

Lerner, who last year refused to answer questions about her role in singling out Tea Party and other conservative groups for extra scrutiny when they applied for tax-exempt status, was called back before the House Oversight and Government Reform Committee on Wednesday. Though Republicans argue she waived her Fifth Amendment right by giving a statement during the last hearing, Lerner continued to invoke that right on Wednesday.

"On the advice of my counsel, I respectfully exercise my Fifth Amendment right and decline to answer that question," she said in response to several questions.

But ranking Democratic Rep. Elijah Cummings, D-Md., got into a heated argument with Chairman Darrell Issa, R-Calif., after Issa tried to adjourn the hearing.

Issa at first stood up and prepared to leave as Cummings said he wanted to ask a "procedural question." In seconds, tensions flared.

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

Issa, Cummings clash at hearing after ex-IRS official Lerner takes 5th | Fox News