The Justice Department has rebuffed a House Republican’s plan to hold an oversight hearing this Thursday featuring a key criminal investigator from the team reviewing mishandling of tax-exempt status applications by the Internal Revenue Service.

Rep. Jim Jordan, R-Ohio, asked Justice attorney Barbara Bosserman on Jan. 28 to testify “due to the administration’s failure to provide necessary information about its IRS investigation.” Bosserman, who is a leader in the Justice investigation into the IRS controversy, has donated money to President Obama’s political campaigns, which GOP lawmakers including Jordan believe represents a conflict of interest. Bosserman is a career attorney; career employees are allowed to donate money to political candidates.

The Feb. 6 House Oversight and Government Reform Committee hearing is titled, “The IRS Targeting Investigation: What is the Administration Doing?”

But Bosserman will not appear, said Deputy Attorney General James Cole in a Jan. 30 reply to Jordan, as published in a tax-exempt organizations newsletter edited by attorney Paul Streckfus.

“The department’s longstanding policy, applied across administrations, is to decline to provide Congress with non-public information about ongoing criminal investigations,” Cole wrote. “This policy is intended to protect the effectiveness and integrity of the criminal justice process, as well as the privacy interests of third parties. It also is founded upon our commitment to avoiding any perception that our law enforcement efforts are subject to undue influence from elected officials.”

Jordan wrote back to Bosserman on Jan. 31 asking that the department reconsider. “The committee recognizes that there may be particular law-enforcement aspects of the investigation that the department is unwilling to discuss publicly. However, there is no legitimate basis for a blanket refusal to answer questions about an apparent conflict of interest and the overall integrity of the investigation.

Republicans in both the House and Senate last month expressed frustration at leaked reports that the FBI and Justice are not likely to pursue criminal charges against IRS employees who delayed processing of applications by largely conservative nonprofits. The Washington Times, however, on Jan. 29, reported that Attorney General Eric Holder said he has not ruled out criminal charges.

Other Republicans, meanwhile, continue pressing the IRS story. House Ways and Means Committee Chairman Dave Camp, R-Mich., on Friday wrote to Treasury Department Secretary Jacob Lew and IRS Commissioner John Koskinen asking for all internal documents relating to the release last November of proposed rules aimed at clarifying the criteria with which the IRS Exempt Organizations Division should review applications from nonprofit groups to balance the mission of social welfare activity and political campaigning. The documents are due Feb. 13.

Koskinen has agreed to testify Wednesday before the Ways and Means Oversight subcommittee on the proposed regulations, the Justice Department probe, his agency’s implementation of the 2010 Affordable Care Act and ongoing efforts to curb improper payments.

“The IRS carries out the critical function of collecting federal revenue—this is why it is alarming that its priorities have gone so far astray, said Ways and Means Oversight subcommittee Chairman Charles Boustany, R-La.

“Improper payments and identity theft continue to be major challenges for the agency and yet the IRS devotes more than 800 employees and millions of dollars to Obamacare implementation,” Boustany said. “It has acknowledged targeting groups based on their personal beliefs, but now is using that scandal to justify new proposed regulations that will silence the very groups that were abused. The problems at the agency are many, and they are diverse, but what they all have in common is it will be up to Commissioner Koskinen to begin correcting them,” he said.