Hundreds of Department of Justice attorneys and other employees have committed "reckless" and "intentional" violations, most of which were never made public, according to a new report by the Project on Government Oversight based on findings from the Justice Department's Office of Professional Responsibility.

POGO reviewed 12 fiscal years of reports of wrongdoing, including misleading courts, violating constitutional rights, "overzealous prosecution," and failure to provide critical information to defendants.

Of 650 such incidents substantiated since 2002, more than 400 were characterized as reckless or intentional, rather than simply poor judgement or error.

The names of the offending employees and the charges aren't publicly released, and in some cases, neither are the reports themselves.

Instead, DOJ's Office of Professional Responsibility investigates allegations internally and hands them off to DOJ management, which can put a gentler spin on the findings, according to POGO. OPR ultimately reports to the attorney general.

“The lack of transparency insulates the Justice Department from meaningful public scrutiny,” said POGO Executive Director Danielle Brian.

“Our findings raise serious concerns that the Attorney General’s Office isn’t aggressively overseeing or disciplining its bad apples,” Brian said.

One major case of prosecutorial misconduct was the 2008 corruption trial of former Alaska Sen. Ted Stevens, who was found guilty of failing to disclose gifts from an oil services provider.

The verdict was set aside in 2009 after a whistleblower alleged that DOJ prosecutors kept evidence from Stevens' attorneys.

Stevens lost his subsequent bid for re-election, and as of April 2013, only one DOJ prosecutor has served a portion of a suspension for his role in the case.

The investigation into Stevens' case was made public by the Senate Judiciary Committee in 2012.

"There is no way to know whether Stevens would have been found guilty if the Justice Department had met its legal obligations to share potentially useful evidence with the defense. As in other cases, prosecutorial misconduct tarnished a case that might have had merit," POGO said.

In another instance, an immigration judge showed bias, made disparaging remarks, and violated procedural standards in cases where defendants were fighting deportation.

Other instances of misconduct uncovered in the report included:

- 48 allegations that attorneys misled courts, including 20 OPR determined were intentional

- 29 allegations that prosecutors failed to provide exculpatory information to defendants, including one OPR determined was intentional

- 13 allegations that employees violated constitutional or civil rights

- 4 allegations of abuse of authority, or "general prosecutorial misconduct," three of which OPR found were intentional

- 1 instance of "overzealous prosecution"

Handing authority for these investigations to the DOJ's independent Office of the Inspector General, instead of OPR, could increase transparency and ensure violators are punished, according to POGO.

The IG only has authority over non-lawyers under current law.

"The DOJ OIG should be given the explicit authority to investigate allegations of misconduct throughout the agency like all other OIGs," the report said. "It’s time to end this wrong-headed exception and to create more independent oversight of and accountability for DOJ attorneys."

Sen. Mike Lee, R-Utah, introduced a bill Thursday that would allow the IG to investigate these cases by giving the watchdog jurisdiction over the entire department.

“The rules that apply to inspectors general in other federal agencies should apply at the Department of Justice,” Lee said in a statement.

“Current law invites undue influence from the attorney general’s office into the process and should be changed to ensure the integrity of investigations of misconduct within the Justice Department.”