The report has been published on the commission's website. It says the department has failed to cooperate with the investigation and left open the question of whether political interference played a role in limiting action against the New Black Panther Party.
Two lawyers who formerly worked in the department's Voting Rights section have described hostility from senior officials and career attorneys to pursuing Voting Rights Act accusations against minorities who harass white voters.
The department has repeatedly denied that race played any role in its handling of the 2008 incident in Philadelphia.
The department investigated complaints that New Black Panther Party leaders King Samir Shabazz and Jerry Jackson intimidated white voters at a Philadelphia polling place. A criminal investigation into the episode was dropped by the Bush administration, but the Justice Department under Obama obtained a narrower civil court order against the conduct than Bush officials sought.
Evidence obtained by the commission puts the department's "version of events into serious doubt," says the report. It relies heavily on the testimony of former Voting Rights lawyers Christopher Coates and J. Christian Adams.
The commission adopted the report by a 5-2 vote when it met on November 19, but did not immediately make it public. The Republican and independent appointees voted to adopt the report, while the two Democratic appointees voted against it.
Abigail Thernstrom, a Republican appointee who has been critical of the commission's inquiry, was absent.
Thernstrom has said accusations against the department are overblown, especially considering that there is no evidence that the presence of the New Black Panther leaders scared anyone away from voting.