Follow @SCMP_News The US tax official at the centre of the storm over the collection agency's targeting of conservative groups told Congress yesterday that she had done nothing wrong and then invoked her constitutional right to refuse to answer lawmakers' questions. In one of the most electric moments since the scandal began nearly two weeks ago, Lois Lerner defended herself before the House Oversight and Government Reform Committee. The panel is investigating the agency's targeting of tea party and other conservative groups seeking tax-exempt status. Lerner oversees the office that processes applications for that status. "I have done nothing wrong," said a stern-looking Lerner, sitting next to three other witnesses and reading from a written statement. "I have not broken any laws. I have not violated any IRS rules or regulations and I have not provided false information to this or any other committee. I am very proud of the work that I have done in government." The IRS is the Internal Revenue Service. I have not broken any laws. I have not violated any IRS rules or regulations and I have not provided false information to this or any other committee. I am very proud of the work that I have done in government Lerner then said she would invoke her constitutional right to avoid incriminating herself. Nine minutes after she began speaking, Darrell Issa, the Republican committee chairman, excused her and Lerner left the hearing, escorted by her lawyer and several other men. The men quickly whisked Lerner into an elevator, where several of the men pushed back television camera crews. Congresswoman Elijah Cummings, the top Democrat on the panel, expressed disappointment that Lerner would not shed light on what she knew about the abuse, and when. Another Democrat, Stephen Lynch, vented his frustration by threatening that continued stonewalling by IRS officials - who have refused to name anyone directly involved in the abuse or say whether more senior officials knew about it - will leave Congress "no alternative" but to appoint a special prosecutor to investigate the wrongdoing. Republicans have used the scandal to attack President Barack Obama as he tries to push through his legislative agenda ahead of next year's elections for Congress. The row also has breathed new life into the tea party movement, whose influence had been waning.