WASHINGTON (CNN) -- A huge increase in workload, rather than deliberate targeting, led to "foolish mistakes" and the political discrimination in the Internal Revenue Service cited by an inspector general's report, the agency's outgoing commissioner said Friday.
The testimony by Steven Miller, who was forced to announce his resignation this week as acting IRS commissioner, came at the first congressional hearing on the matter that has put President Barack Obama's administration on the defensive.
Rep. Dave Camp, chairman of the Republican-led panel, and other GOP members sought to depict the controversy as indicative of government gone wild, with the IRS abusing conservative groups and other political foes of the administration.
Democrats on the committee also expressed outrage at the political targeting of conservative groups seeking tax-exempt status, but they noted that the top IRS official at the time was appointed by Republican President George W. Bush, not Obama.
They also noted that the inspector general's report stated that there was no evidence of any political motivation or influence from outside the IRS.
In his opening remarks, Miller described an IRS division that handles requests for tax exempt status by political groups as overwhelmed by a surge that followed the Supreme Court's 2010 Citizens United decision, which greatly expanded the ability of corporations, unions and other organizations to participate in election spending, though not through direct contributions to candidates or parties."I think that what happened here was that foolish mistakes were made by people who were trying to be more efficient in their workload selection," Miller said, calling the practices described in the inspector general's report as "intolerable" and a "mistake," but "not an act of partisanship."
He apologized for what he later called "horrible customer service," but he also stubbornly rejected any accusation that it amounted to politicizing the work of the IRS.
Miller underwent aggressive and accusatory questioning from Camp and other Republicans, who claimed he misled Congress by failing to reveal the extent of the problem at previous hearings dating back a year.
"When asked the truth and you know the truth and you have a legal responsibility to inform others of the truth but you don't share that truth, what is that called?" Camp asked.
"I always answer questions truthfully, Mr. Camp," Miller replied.
GOP Rep. Paul Ryan of Wisconsin, the unsuccessful vice presidential candidate in last year's election, later asked how the panel could accept Miller's repeated claim that he never misled the committee, despite the Republican assertions he previously failed to notify it about the problem.
Miller responded: "I did not mislead the committee" and added that the controversy was not politically motivated.
When asked by GOP Rep. Devin Nunes of California why he resigned if he wasn't personally involved in the improper acts, Miller replied: "I resigned because as the acting commissioner, what happens in the IRS, whether I was personally involved or not, stopped at my desk."
"And so, I should be held accountable for what happens," Miller said. "Whether I was personally involved or not, a very different question, sir."
During a break, Camp told reporters that he wasn't satisfied with Miller's testimony so far, but refrained from a final assessment pending the remainder of the hearing. Camp added the panel wanted to get unspecified records from Miller's tenure at the IRS.
Democrats sought to balance their rejection of any perception of political manipulation by the IRS with an effort to portray the situation as a poorly managed increase in demand for tax exempt status by political groups.
Rep. Jim McDermott, D-Washington, said the vast majority of the increased applications for tax exempt status after the Citizens United decision were from "far right groups," while fellow Democratic Rep. Richard Neal of Washington said the conservative organizations wanted to be involved politically without revealing donors -- as allowed for the 501 (c) (4) groups under the federal tax code.
"It all started right after Citizens United," he said, adding that political groups "saw the door open" and thought that "we can get in, we can do political advertising."
McDermott said there is a difference between "stupid mistakes and deliberate mistakes," adding that the IRS officials handling the requests took a shortcut "they deeply regret."
Democrats repeatedly asked the other witness Friday -- Inspector General J. Russell George, who wrote the report on the controversy -- to reiterate that there was no evidence of political motivation.
Rep. Sander Levin, the panel's ranking Democrat, specifically cited the former IRS commissioner, Douglas Shulman, for what he called misleading Congress on the issue. Shulman was not a witness at Friday's hearing, but is scheduled to appear at other congressional hearings next week.