"This timeline reveals at least two extremely unethical actions by the IRS. One, as early as 2010, they targeted groups for political purposes. Two, they willfully and knowingly lied to Congress for years despite being aware that Congress was investigating this practice," Boustany said.
"This is an outrageous abuse of power. Going after organizations for referencing the Bill of Rights or expressing the intent to make this country a better place is repugnant," Boustany added. "There is no excuse for this behavior."
Several congressional committees have promised investigations, including the Ways and Means Committee, which plans to hold a hearing.
"The admission by the agency that it targeted American taxpayers based on politics is both shocking and disappointing," said Rep. Dave Camp, R-Mich., chairman of the Ways and Means Committee. "We will hold the IRS accountable for its actions."
The group Tea Party Patriots said the revelation was proof that the IRS had lied to Congress and the public when Schulman said there had been no targeting of tea party groups.
"We must know how many more lies they have been telling and how high up the chain the cover-up goes," Jenny Beth Martin, national coordinator for the group Tea Party Patriots, said in a statement Saturday.
"It appears the IRS committed crimes and violated our ability to exercise our First Amendment right to free speech. A simple apology is not sufficient reparation for violating the constitutional rights of United States citizens. Therefore, Tea Party Patriots rejects the apology from the Internal Revenue Service," Martin said. "We are, however, encouraged to hear that Congress plans to investigate. Those responsible must be held accountable and resign or be terminated for their actions."
On Friday, White House spokesman Jay Carney said the administration expected the inspector general to conduct a thorough investigation, but he brushed aside calls for the White House itself to investigate.