Lois Lerner, who heads the IRS division on tax-exempt organizations, declined to testify on constitutional grounds but issued a statement saying she had not done anything wrong.
"While I would very much like to answer the committee's questions, I have been advised [by counsel] ... to invoke my right [against self-incrimination]," Lerner said when she appeared before the House Oversight and Government Reform Committee.
Attorney William Taylor told the committee in a letter his client would not answer questions following accusations by the panel's Republican leaders Lerner had lied to them.
Lerner committed no crime nor made any misrepresentations, the letter said. But "under the circumstances she has no choice but to take this course."
When Lerner first apologized for the targeting of conservative groups seeking tax-exempt status on May 10, she told reporters she learned of the improprieties from news reports in early 2012.
But a Treasury Department inspector general's audit found she knew about the targeting much earlier and tried to cleanse the practice by broadening the efforts to include liberal groups.
"The committee has been contacted by Ms. Lerner's lawyer, who stated that his client intended to invoke her Fifth Amendment right and refuse to answer questions," committee spokesman Ali Ahmad said Tuesday.
Acting IRS Commissioner Steven Miller and former IRS Commissioner Douglas Shulman both testified before the Senate Finance Committee Tuesday.
Deputy Treasury Secretary Neal S. Wolin also was testifying Wednesday. He has said he learned of the inspector general's audit into the targeting last summer. Republicans have said they want him to explain what he did with that information.
Miller and Shulman, a George W. Bush appointee who left the job Nov. 9, told the Senate panel they never discussed the targeting with administration officials outside the agency during the 2012 campaign year.
Miller also offered new details about how Lerner came to disclose the results of the inspector general's report at a May 10 bar association event.
Miller told senators Tuesday he planted the question at the closed-door meeting with tax lawyers that prompted Lerner's revelation.
He also said IRS officials were talking about disciplining Lerner.