"We should have been more diligent in our responsibility to the American taxpayer and to the American public," Fink said when pressed by Chaffetz.
The congressman repeatedly asked Fink when he became aware of the cost of the conference, which the inspector general said was one of 225 events that the IRS spent $50 million on from 2010 through 2012.
Fink responded: "I actually did not become aware of the massive expense until much later. I did not know what the expense was at the time of the conference that we were paying."
That turned out to be untrue.
An investigator with the inspector general's office noted Fink signed off on the estimated costs of the event, which were $4.3 million, roughly $200,000 more than the IRS ended up spending.
Fink then corrected his testimony to say he did sign "the routing slip."
A visibly frustrated Chaffetz pointed out the inconsistency in Fink's testimony and asked: "Are you here claiming no responsibility at this point?"
"Absolutely not. That's why I am here," Fink said.
Thursday's hearing comes as the Congress continues to probe the actions of the IRS, and follows another inspector general report that another section of the taxing agency inappropriately targeted conservative political groups seeking tax-exempt status.
That revelation led President Barack Obama to remove the acting commissioner of the agency.
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