It has been over a year since disgraced former Internal Revenue Service official Lois Lerner staged an apology for the IRS's targeting of conservative nonprofits.

Since then, the House of Representatives, including the Oversight and Government Reform Committee on which I serve, has conducted a vigorous and extensive investigation.

Despite uncovering a great deal of information about the IRS’s targeting — even without testimony from Ms. Lerner — the simple fact is this:

Congress cannot hold the wrongdoers to account through the criminal justice system. And that is why we need a serious criminal investigation by President Obama's administration, which is charged by the Constitution with faithfully executing the nation's laws.

Only the Department of Justice has the ability to prosecute crimes. Only the Justice Department can empanel a federal grand jury. Only the Justice Department can bring a federal indictment.

Last spring, the president and Attorney General Eric Holder expressed outrage about the IRS targeting, which systematically sidelined conservative groups from exercising their First Amendment rights. Holder pledged a thorough criminal investigation.

Alas, since then, we have seen no progress in DOJ’s criminal investigation. Time and again, the Justice Department has refused to update Congress on its investigation.

The more we learn about the department’s investigation, however, the more we become convinced that the department is conducting an investigation designed to fail.

Americans have serious cause for concern.

Earlier this year, we learned the investigation is being led by Barbara Bosserman, an attorney in the Department’s Civil Rights Division.

According to public records, Bosserman is a substantial contributor to Obama and the Democratic National Committee. This conflict of interest is staggering, and blatantly violates internal Justice Department regulations.

In recent days, however, we learned that the Department’s Public Integrity Section — which Holder has said is conducting the criminal investigation with the Civil Rights Division — also has a massive conflict of interest.

In October 2010, in response to concerns about the Supreme Court's Citizens United decision, Jack Smith, the chief of the Public Integrity Section, brokered a meeting with Lerner to discuss how she could help the Obama administration enforce campaign-finance laws against nonprofit groups.

The Justice Department’s coordination with Lerner came just days before she told a Duke University crowd of the pressure on the IRS to “fix the problem” caused by the Supreme Court’s Citizens United decision.

The same Jack Smith that pressured the IRS in 2010 to crack down on nonprofit groups now supervises the investigators from the Public Integrity Section who are involved in the Department’s criminal investigation of the IRS targeting.

In other words, the Obama administration’s criminal investigation of politically-driven malfeasance is led by a contributor to Obama’s campaign and supervised by an individual who pressured the IRS in 2010 to assist in the potential criminal enforcement of nonprofit groups engaged in political speech.

It is no wonder that anonymous law-enforcement officials leaked to the Wall Street Journal that no criminal charges would be filed.

Yet when asked whether the Attorney General would appoint a special prosecutor, a senior Department official told Congress: “[N]o, a special counsel is not warranted.”

The House recognizes just how serious this investigation is to restoring the public trust in the IRS. Earlier this month, the House passed a resolution I sponsored urging Holder to appoint a special prosecutor to independently investigate the IRS targeting.

This resolution passed with a strong majority of the House, with 26 Democratic Members joining in support.

Twenty-six members of the president’s own party disagree with his statement that there is “not even a smidgeon of corruption” in the IRS targeting.

Twenty-six Members of the attorney general’s party believe that his investigation has been compromised by conflicts of interest and politicized leaks.

Congress’s strong, bipartisan voice calling for a special prosecutor to investigate the IRS targeting should be a clear signal to the Obama administration that Americans have lost faith in its investigation.

The simplest way for the attorney general to restore that faith and ensure a thorough investigation is to appoint an independent special prosecutor.

Only then can the American people have any confidence that the IRS wrongdoers will be fully held to account for their criminal acts.

Rep. Jim Jordan, R-Ohio, is chairman of the economic growth, job creation and regulatory affairs subcommittee of the House Oversight and Government Reform Committee.