Attorney General Eric Holder put a significant donor to President Obama's campaigns in charge of the Justice Department's probe into the IRS's targeting of Tea Party groups, Rep. Darrell Issa, R-Calif., claimed in a letter Wednesday. According to Issa, the person running the probe is DOJ attorney Barbara Bosserman, who has donated more than $6,000 total to the Obama campaigns in 2008 and 2012.

Issa is chairman of the House Oversight and Government Reform Committee, and the Republican Party's leading watchdog in the House. In the Wednesday letter to Holder, Issa said his committee had learned of Bosserman's role from "several current and former IRS officials whom both the committee and the department have interviewed."

In addition to the more than $6,000 to Obama'a campaigns, Bosserman has donated $650 to the Democratic National Committee since 2004, records show. Issa said this called into question her ability to be impartial.

"By selecting a significant donor to President Obama to lead an investigation into the inappropriate targeting of conservative groups, the department has created a startling conflict of interest. We request that you immediately remove Ms. Bosserman from the ongoing investigation," Issa said in the letter. The letter was also signed by Rep. Jim Jordan, R-Ohio. They also requested a "comprehensive explanation" of why she was chosen to head up the probe.

Justice Department spokeswoman Dena Iverson would neither confirm nor deny that Bosserman was indeed heading up the probe. In an email to the Washington Examiner, she said: "It is contrary to department policy and a prohibited personnel practice under federal law to consider the political affiliation of career employees or other non-merit factors in making personnel decisions. Additionally, removing a career employee from an investigation or case due to political affiliation, as Chairmen Issa and Jordan have requested, could also violate the equal opportunity policy and the law."