White House spokesman Jay Carney said he did not know when administration officials learned of the practice.
The IRS apologized Friday for targeting groups because they included the words "tea party" or "patriot" in their applications for tax-exempt status. The agency—led at the time by a Bush appointee—blamed low-level employees, saying no high-level officials were aware.
Senate Republican Leader Mitch McConnell of Kentucky called on the White House to investigate. Carney said the matter already was being investigated by an inspector general.