WASHINGTON - At various points over the last two years, Internal Revenue Service officials targeted nonprofit groups that criticized the government and sought to educate Americans about the U.S. Constitution, according to documents in an audit conducted by the agency's inspector general.

The documents, obtained by the Washington Post from a congressional aide with knowledge of the findings, show that on June 29, 2011, IRS staffers held a briefing with senior agency official Lois G. Lerner in which they described giving special attention to instances where "statements in the case file criticize how the country is being run." Lerner, who oversees tax-exempt groups for the agency, raised objections and the agency revised its criteria a week later.

But six months later, the IRS applied a new political test to groups that applied for tax-exempt status as "social welfare" groups, the document says. On Jan. 15, 2012, the agency decided to target "political action type organizations involved in limiting/expanding Government, educating on the Constitution and Bill of Rights, social economic reform movement," according to the appendix in the IG report, which was requested by the House Oversight and Government Reform Committee and has yet to be released.

The new revelations are likely to intensify criticism of the IRS, which has been under fire since agency officials acknowledged they had deliberately targeted groups with tea party or patriot in their name for heightened scrutiny.

During an appearance Sunday on CNN's State of the Union, Sen. Susan Collins (R., Maine) described the practice as "absolutely chilling" and called on President Obama to condemn the effort.

"I just don't buy that this was a couple of rogue IRS employees," she said. "After all, groups with progressive in their names were not targeted similarly."

If it were just a small number of employees, she said, "then you would think that the high-level IRS supervisors would have rushed to make this public, fired the employees involved, apologized to the American people and informed Congress. None of that happened in a timely way."

House Oversight and Government Reform Committee Chairman Darrell Issa (R., Calif.), told NBC's Meet the Press Sunday that he's not satisfied with the Obama administration's handling of the controversy. The IG report was "leaked by the IRS to try to spin the output," Issa said, and lawmakers now need to go through the full report so they can "see what the instituted changes need to be to make this not happen again."

The agency did not appear to adopt a more neutral test for social welfare groups - which file for tax-exempt status under section 501(c)(4) of the tax code - until May 17, 2012, according to the timeline in the inspector general's report.

At that point, the IRS again updated its criteria to focus on "organizations with indicators of significant amounts of political campaign intervention (raising questions as to exempt purpose and/or excess private benefit.)"

White House press secretary Jay Carney said that if the inspector general "finds that there were any rules broken or that conduct of government officials did not meet the standards required of them, the president expects that swift and appropriate steps will be taken to address any misconduct."