Horowitz's report examined actions taken by top officials before the 2016 election, including the handling of the investigation into Clinton's use of a private email server when she was secretary of state.
Comey already has been criticized for waiting a month to act during the 2016 presidential election campaign after thousands of emails were discovered on Weiner's laptop that appeared to be relevant to the Clinton investigation.
The president "is really anxious to see the report", said a person familiar with the planned Thursday briefing. Supporters from both parties regard him as apolitical.
Lavinsky noted that Justice Department officials had similarly briefed the Obama White House in 2012 upon completion of its report on the scandal involving the gunrunning project known as Operation Fast and Furious.
The IG's report is expected to be over 500 pages.
Trump has expressed great interest in the inspector general's report, as well as some skepticism it might not be as damning as he hoped. He denies those charges.
The media outlet obtained an early copy of the report that's expected to be released later in the afternoon.
Law enforcement officials previously told Reuters the information was leaked to former New York Mayor Rudy Giuliani, an adviser to the Trump campaign.
"We did not find documentary or testimonial evidence that improper considerations, including political bias, directly affected the specific investigative actions we reviewed", Horowitz said in the report to be issued Thursday.
The exhaustive review of a momentous period in the department's history is expected to criticize Comey's handling of the investigation at key junctures for violating departmental norms. That decision came after the recommendation of Sessions himself, which was in turn informed by Deputy Attorney General Rod Rosenstein.
Lynch described that meeting as a chance encounter unrelated to the case, but Clinton's critics seized on it to question Lynch's objectivity.
The report also examined the conduct of Federal Bureau of Investigation officials Peter Strzok and Lisa Page, who also worked on Special Counsel Robert Mueller's "Russiagate" probe. Then, two days before the November 8 election, he told lawmakers the team had found "no new classified" emails. We may not know that for a year or more, but it does appear that Horowitz is leaving that possibility open.
Comey has claimed in testimony before Congress that he cut Lynch out of the loop because he considered her compromised in relation to the Clinton probe.
Clinton has since said that Comey's letter contributed to her unexpected defeat by Trump. "And I could be wrong, but we honestly made a decision between those two choices that even in hindsight - and this has been one of the world's most painful experiences - I would make the same decision". "Right?!" Page wrote to Strzok. But Jill McCabe received those donations from a PAC affiliated with then-Democratic Virginia Gov. Terry McAuliffe before McCabe oversaw the Clinton probe. Trump has repeatedly cited the contributions in denouncing McCabe.
A document listing preliminary conclusions was obtained by The Associated Press ahead of a separate report from the Justice Department's internal watchdog.