The Internal Revenue Service Building is shown July 22, 2013 in Washington, D.C. (Win McNamee/Getty Images)

A conservative group suing the Internal Revenue Service on Monday amended its lawsuit over the agency’s processing of its request for tax-exempt status to include the agency’s chief counsel, William Wilkins.

Acting on behalf of True the Vote , a Houston-based voter watchdog group, the ActRight Legal Foundation first asked the U.S. District Court for the District of Columbia in late May to grant its request for tax-exempt status and award damages for what it described as unlawful conduct by the IRS.

Last week, House Oversight and Government Reform Committee Chairman Darrell Issa (R-Calif.) released a transcript in which an IRS employee said Wilkins helped develop its controversial guidelines for reviewing tax-exempt applications the agency dubbed “tea party” cases. The IRS said last week that Wilkins, one of only two IRS officials appointed by the president, was never involved in the process.

The panel’s ranking Democrat, Rep. Elijah E. Cummings (Md.), has questioned whether conservative groups were actually singled out for special scrutiny by the IRS, citing repeated testimony by agency employees that partisanship played no role in the program.

The lawsuit also added five senior IRS employees — four of whom were working at headquarters, one of whom was based in Cincinnati. The amended suit also includes a new count accusing IRS employees and senior leaders of violating key portions of the Administrative Procedures Act, which prohibits federal employees from violating constitutional rights and exceeding their authority in the carrying out of their official duties.

“This lawsuit is the only way to get all of the answers involving this national scandal,” True the Vote President Catherine Engelbrecht said in a statement. “Our goal is not a speedy settlement or a quiet Washington deal. We will sue, depose and expose every person who came near this illegal scheme to suppress voters’ First Amendment rights. The American people — not just True the Vote — deserve answers.”

True the Vote, which was founded in June 2010 and has been accused by Democrats of intimidating African American voters, is affiliated with the King Street Patriots, a tea party group.

The IRS declined to comment on the suit Monday.