Former Internal Revenue Service official Lois Lerner was the administrator at the center of the scandal over handling of tax-exemption applications. (Lauren Victoria Burke/AP)

No criminal charges will be filed in the two-year investigation into whether any Internal Revenue Service officials, including Lois Lerner, committed crimes in connection with the handling of tax-exemption applications by conservative groups, the Justice Department announced Friday.

“Our investigation uncovered substantial evidence of mismanagement, poor judgment and institutional inertia, leading to the belief by many tax-exempt applicants that the IRS targeted them based on their political viewpoints,” Assistant Attorney General for Legislative Affairs Peter J. Kadzik wrote in an eight-page letter to Rep. Bob Goodlatte (R-Va.), chairman of the House Judiciary Committee, and Rep. John Conyers Jr. (D-Mich.)

“But poor management is not a crime,” Kadzik wrote. “We found no evidence that any IRS official acted on political, discriminatory, corrupt, or other inappropriate motives that would support a criminal prosecution.”

Kadzik said that the Justice Department’s criminal and civil rights divisions, working with the FBI and the Treasury inspector general for tax administration, conducted an “exhaustive probe,” interviewing more than 100 people, collecting more than 1 million pages of IRS documents, analyzing nearly 500 tax-exemption applications and examining the role and potential culpability of “scores of IRS employees.”

“We also found no evidence that any official involved in the handling of tax-exempt applications or IRS leadership attempted to obstruct justice,” Kadzik said.

The Justice Department’s decision closes the long-running investigation launched after a Treasury inspector general audit report revealed the IRS’s mishandling of tax-exempt applications that it suspected to be involved in political activity.

The audit said that one way that the IRS identified groups for review was through keywords, such as “Tea Party” and “Patriots,” and the inventory of the applications identified for review was internally referred to as the “Tea Party cases.”

The audit set off a firestorm on Capitol Hill, with allegations by congressional Republicans that the IRS targeted mostly conservative groups, including the tea party, for deeper review of their applications for tax-exempt status.

Lerner, the administrator at the center of the IRS scandal, was held in contempt of Congress last year after she refused to testify and answer questions about the allegations.

In a statement on Friday, Rep. Darrell Issa (R-Calif.) criticized the Justice Department’s decision not to bring charges as “giving Lois Lerner a free pass” and called it “a low point of accountability in an Administration that is better known for punishing whistleblowers than the abuse and misconduct they expose.”

“After stating that their investigation confirms that Tea Party and conservative groups were improperly targeted, they dismiss it merely as a byproduct of gross mismanagement and incompetence — ignoring volumes of evidence in the public record and efforts to obstruct legitimate inquires,” Issa said in the statement.

Conyers, the ranking member of the House Judiciary Committee, called on Republicans to “end this partisan witch hunt and focus on matters that impact the lives of the American people.”

“The Department’s findings confirm what we have known since the self-proclaimed ‘conservative Republican’ manager in Cincinnati explained more than two years ago that the IRS did not target conservative groups for political reasons and took no direction from the White House,” Conyers said in a statement.“This is also consistent with the conclusions of two Inspector General reports and multi-year House and Senate Congressional investigations, including a recent bipartisan report from the Senate Finance Committee.”