In a letter sent today, Rep. Darrell Issa, Chairman of the House Oversight and Government Reform Committee, accuses ranking member Rep. Elijah Cummings of acting as if he were a defense attorney for former IRS employee Lois Lerner. He also argues that Lerner could face contempt proceedings for her refusal to testify to the Committee last week.

In a letter directed to Cummings, Issa writes “you have made yourself an obstacle to effective congressional oversight, in effect, a defense counsel for Lerner and others who acted to deprive Americans of their constitutionally guaranteed rights.”

The letter is part of an ongoing debate between Republicans and Democrats on the Oversight Committee over whether or not Lerner properly invoked her 5th amendment right not to testify when she appeared before the Committee last May.

Issa’s letter, dated Friday the 14th, is a response to claims made earlier this week by Cummings and his attorney. In his own letter, Cummings argued Lerner can not be held in contempt because she did not receive clear notice that her 5th Amendment privilege claim had been rejected by the Committee.

In response, Issa points out several clear instances where Lerner (and Rep. Cummings) were notified that the Committee had voted to reject Lerner’s claim last year. He writes “In a letter to Lerner’s counsel on February 25, 2014, on which you were copied, I wrote ‘[B]ecause the Committee explicitly rejected [Lerner’s] Fifth Amendment privilege claim, I expect her to provide answer when the hearing reconvenes on March 5th.'”

In a 90 page Oversight Committee staff report published earlier this week, Issa argued in more detail that Lerner, who was under subpoena to appear last May, had waived her right to assert the 5th by making a statement proclaiming her innocence and then authenticating a document before she invoked the Fifth Amendment. A few weeks later, on June 28, 2013, the Committee voted that Lerner had waived her privilege. That eventually led to her being called back before the Committee for a second time last week. But Lerner refused to comply and once again asserted her 5th Amendment right not to testify.

All of this legal wrangling was overshadowed last week by Rep. Cummings histrionics during the meeting and Rep. Issa’s decision to cut off Rep. Cummings’ microphone rather than let him express his outrage. Rep. Issa has since apologized for cutting off the microphone.