Issa: IRS frustrating congressional investigations

House Oversight Chairman Darrell Issa (R-Calif.) warned the IRS commissioner on Tuesday that the agency’s slow response to his document requests were frustrating the committee’s investigation into the IRS targeting controversy.

Issa’s letter came the day before the IRS commissioner, John Koskinen, is scheduled to testify before the committee about how the agency has responded after it admitted singling out Tea Party groups last May.

In all, Issa lays out 11 requests he says haven't been fulfilled.

Among them are all communications involving key IRS officials like Lois Lerner and Holly Paz from 2009 until August 2013. Issa also wants any emails from IRS employees to the White House, and any communications discussing new rules for 501(4) tax-exempt groups.

"The IRS's continued failure to fully satisfy the committee's requests frustrates the committee's investigation and delays the completion of the committee's fact-finding work," Issa wrote to Koskinen. "Your continued noncompliance with these requests also contravenes your pledge to fully cooperate with congressional investigations."

Koskinen told reporters in the Capitol on Tuesday that he looked forward to appearing before Oversight, and that he hoped the agency could offer any assistance it could to the six congressional investigations currently underway.

"We'll figure out what the facts are, and move on accordingly," Koskinen said. "I'm sure we'll have a meaningful exchange tomorrow on where the investigations are. Our goal is to be cooperative to all the investigators, and get them the information they need."