President Obama said the acting commissioner of the Internal Revenue Service resigned Wednesday and promised that he “will not tolerate” the types of abuses reported by the agency’s inspector general. Speaking from the East Room of the White House, the president promised to “hold the responsible parties accountable” and said the administration “will work with Congress” on their investigations.

The agency’s acting commissioner, Steven Miller blamed two “rogue” employees in the Cincinnati IRS office for targeting conservative groups, but Obama said that Treasury Secretary Jack Lew had requested and received Miller’s resignation Wednesday. The political abuses were “inexcusable,” the president said.

The IRS scandal erupted into headlines last week after an agency official admitted  Tea Party groups were targeted for intrusive reviews of applications for non-profit status. An inspector general’s report said “inappropriate criteria” were used to target the groups, which experienced unreasonable delays in processing their applications, and were wrongly asked to identify their donors. Leaked information from Mitt Romney‘s tax records was used to attack the Republican candidate during last year’s presidential campaign. Two groups connected to the famed evangelist Billy Graham were also reportedly targeted by the IRS.

A veteran executive within the IRS, Miller had previously served as Deputy Commissioner for Services and Enforcement, Commissioner of the Large Business and International Division, Commissioner of the Tax Exempt and Government Entities Division, and other offices, including Chief Counsel. Miller was appointed Acting IRS Commissioner in November, after the reported abuses of conservative groups had ended.