The Justice Department attorney leading the probe into whether the IRS improperly targeted Tea Party groups visited the White House in 2009 as a guest of President Obama, according to official visitor logs.

The visit raises more questions about possible ties between Barbara Kay Bosserman and Obama, after Republican lawmakers complained last week she should not be leading the probe into the IRS.

Campaign finance records show Bosserman has given more than $6,000 to Obama's two presidential campaigns. Citing that support, Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, and Rep. Jim Jordan, R-Ohio, last week called on Attorney General Eric Holder to remove her from the case -- a request the DOJ dismissed.

The White House event which Bosserman attended in October 2009 was listed as a "hate crimes event" with Obama. The president at the time was holding a ceremony in the East Room to sign hate crimes legislation making it a federal crime to assault someone because of their sexual orientation.

Bosserman, as a prosecutor who specializes in hate crimes law, would seem at first blush a natural fit for the event.

But a Justice Department source told Fox News it was "extraordinary" for a career employee to be invited to the White House by the president to participate in an event with him, and Bosserman's attendance would have to have been cleared though the hierarchy of the Civil Rights Division and the Justice Department.

She was listed in the logs as a guest of "Barack Obama/President" -- though, so were dozens of other people at the White House that day. Among the high-profile names in attendance were Thomas Perez, the current Labor secretary who at the time was Bosserman's boss at Justice, and NAACP President Benjamin Jealous.

The Justice source also said it is "extremely odd" that an attorney from the Civil Rights Division was selected for the IRS probe at all. The more logical and typical selection, the source advised, would have been a prosecutor from the Public Integrity unit of the Criminal Division.

However, the Justice Department has pushed back hard on those questioning Bosserman's fitness for the role.

On Monday, a DOJ official told FoxNews.com “the signing ceremony was attended by the team of Civil Rights Division attorneys that worked with Congress on passage of the legislation. That is typical when the department provides technical support on bills.”

Another official told Fox News last week that simply because a trial attorney exercised her constitutional right to make a political donation does not mean she's not acting professionally. Officials stressed that they cannot consider political affiliation when handing out case assignments.

"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," the department said in a statement. "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."

But amid concerns that the Justice Department is slow-walking the probe, Republicans complained last week that the case may be "compromised."

"By selecting a significant donor to President Obama to lead an investigation into inappropriate targeting of conservative groups, the Department has created a startling conflict of interest," Issa and Jordan wrote in their letter to Holder. "It is unbelievable that the Department would choose such an individual to examine the federal government's systematic targeting and harassment of organizations opposed to the President's policies."

Fox News' James Rosen contributed to this report.