(CNN) -- Steven Miller, the outgoing acting commissioner of the IRS, apologized Friday "on behalf of the Internal Revenue Service for mistakes that we made and the poor service we provided." "The affected organizations and the American public deserve better," he said. Miller made the remark at a House and Ways and Means Committee hearing over extra scrutiny that the IRS gave to conservative groups seeking tax-exempt status. Miller, who said partisanship has "no place at the IRS," added that he doesn't believe partisanship motivated anyone who gave the conservative groups extra scrutiny. What happened, he said he believes, was that "foolish mistakes were made by people trying to be more efficient in their workload selection."