Justice Department Inspector General Michael Horowitz said Wednesday he and his team "identified significant concerns" about how the FBI conducted its investigation into Donald Trump's 2016 presidential campaign.

"The activities we found here don't vindicate anybody," Horowitz said when asked about comments made by former FBI chief James Comey, who took a victory lap after the DOJ watchdog released a report this week on the agency's probe of Trump's campaign.

But Horowitz also noted that "opening the investigation was in compliance with [DOJ] and FBI policies, and we did not find documentary or testimonial evidence that political bias or improper motivation influenced" the decision to initiate the Trump-Russia probe.

The DOJ watchdog's remarks came in testimony before the Senate Judiciary Committee, where Chairman Lindsey Graham, R-S.C., one of Trump's closest allies, set the tone of the hearing with a more than 40-minute speech blasting the FBI.

"My goal is to make sure when this is over... you look at this as more than a few irregularities," Graham said. "What happened here is the system failed. People at the highest level of our government took the law into their own hands."