Signaling that it intends to conduct an aggressive investigation into how the Internal Revenue Service targeted certain conservative-leaning groups, the Senate Finance Committee has asked the agency's outgoing acting commissioner to document any communications with top Obama administration officials about the unfolding scandal.

Sens. Max Baucus (D-Mont.), left, and Orrin G. Hatch (R-Utah.) (AP/J. Scott Applewhite)

Sens. Max Baucus (D-Mont.) and Orrin G. Hatch (R-Utah), who lead the Finance Committee, wrote to Steven T. Miller on Monday making 41 specific requests for information. They include documentation of all attempts to elicit information from groups seeking tax-exempt status; a list of all the words and phrases used to target applicants for additional scrutiny; how IRS officials discovered that employees were inappropriately targeting certain groups; and all internal communications between employees working to review the groups.

Additionally, the senators ask Miller for "documents relating to communications between any and all IRS employees and any and all White House employees, including but not limited to, the President, regarding the targeting of organizations" seeking tax exempt status. The senators also want to see "any written communication, memos, policy drafts, or other documents" related to the IRS's consideration of tax-exempt status since 2009.

"These actions by the IRS appear to be a clear breach of the public's trust," the senators wrote in their letter to Miller. "Targeting groups based on their political views is not only inappropriate but it is also intolerable."

Miller, who resigned last week at the request of President Obama, told the House Ways and Means Committee last week that "foolish mistakes" and “horrible customer service” led IRS employees to single out conservative groups seeking tax-exempt status for special scrutiny.

Under almost four hours of intense questioning, Miller said he had recently met with Treasury officials to discuss how the agency had targeted tax-exempt groups, but insisted that he never had contact with White House officials.

“Absolutely not,” Miller said under questioning by Rep. Devin Nunes (R-Calif.).

“How about President Obama’s reelection campaign?” Nunes asked later.

“No,” Miller replied.

Miller even challenged the notion that the groups were “targeted” because they were conservative. Instead, he said, they were “listed” because they were politically active.

Miller is set to testify Tuesday alongside his predecessor, former IRS Comnmissioner Daniel Shulman, and J. Russell George, the Treasury inspector general for tax administration who wrote the audit report detailing how IRS employees improperly targeted certain groups.

On Wednesday, Shulman and George are set to testify before the House Oversight and Government Reform Committee, alongside Treasury Deputy Secretary Neil Wolin. George told the Ways and Means Committee last Friday that he first informed Wolin about his audit during a meeting last summer.

Read the full letter to Miller from the Finance Committee below:

Senate Finance Committee letter to Steven T. Miller (May 20, 2013) by ed_o_keefe_1

Follow Ed O'Keefe on Twitter: @edatpost