Sen. Tom Coburn is not satisfied by the Treasury Department’s ongoing failure to fully comply with his requests for information about conference spending.

In the aftermath of a Treasury Inspector General for Tax Administration report and a follow-up letter from Coburn, the Treasury has

, the Treasury has offered an apology to the Oklahoma Republican for its insufficient response to past questions about IRS spending on conferences, blaming it on a miscommunication.

In a June 6 letter provided by Coburn’s office, Assistant Secretary of the Treasury for Legislative Affairs Alastair M. Fitzpayne wrote that the department and the IRS had received separate queries from House Oversight and Government Reform Chairman Darrell Issa, R-Calif., about conferences, but only a unified request from Coburn.

“During the same time period that we received your request, Treasury and the IRS received similar — but separate — requests from Chairman Issa. Treasury did not include any IRS data in its submission to Chairman Issa because the IRS responded separately. We mirrored this approach in responding to your request, and we informed your staff by email that the data pertained only to Treasury’s Departmental Offices (which does not include the IRS),” Fitzpayne wrote. “We recognize that this may not have been clear, and we apologize for any confusion.”

The Treasury letter included materials that had previously been provided to Issa’s panel. In a response sent Tuesday to Treasury Secretary Jacob J. Lew, Coburn expressed his displeasure with the response.

“This ‘dog ate my homework’ response does not excuse the department from its responsibility to respond fully to all reasonable requests from Congress,” Coburn wrote. “In fact, a response such as this raises questions about whether the department takes any Congressional inquiries seriously as it should.”

He also said that the response was incomplete because he had asked for information about all conferences attended by Treasury Department.

“To date, despite providing ‘guidance on conferences and travel,’ Treasury has still not fully responded to the original request. The letter requested a full listing of every conference attended by an employee of the Treasury Department,” Coburn said. “Treasury has provided a list of five conferences attended over a 7-year period of time, as well as the Anaheim conference in the June 6, 2013, response.”