By Sarah N. Lynch and Mark Hosenball
WASHINGTON (Reuters) - Former FBI Director James Comey deviated from the bureau's norms in a probe into former presidential candidate Hillary Clinton, but there is no evidence his actions before the 2016 election were motivated by political bias, a Justice Department watchdog report concludes, a source familiar with the report said on Thursday.
The report by Inspector General Michael Horowitz says that the FBI's decision not to prosecute Clinton in the case was "consistent with the department’s historical approach in prior cases under different leadership," the source said.
"We found no evidence that the conclusions by the prosecutors were affected by bias, or other improper considerations," the report says, according to the source.
A long-serving law enforcement official, Comey became a controversial figure in the 2016 election, drawing accusations from both Republicans and Democrats that his handling of an investigation into Clinton's emails influenced the campaign.
Comey later headed a separate probe into the Trump campaign's alleged ties to Russia. Trump fired him as head of the FBI in 2017.
The inquiry has focussed on whether public statements made by Comey about Democrat Clinton's use of a private email server while she was secretary of state were based on "improper
In July 2016, Comey held an unusual news conference to explain why the FBI would not be recommending criminal charges against Clinton over her use of the private server, instead of a State Department server, for some official business.
He chastised Clinton for being "extremely careless" but said there was insufficient evidence to charge her with a federal crime. That upset Republicans who said Comey's statement could have helped Clinton's election campaign.
But in October 2016, less than two weeks before Election Day, Comey sent members of Congress a letter disclosing that the probe was being reopened after new emails were found on the computer of the husband of top Clinton aide Huma Abedin.
Clinton has since said that Comey's letter contributed to her unexpected defeat by Trump. Two days before the Nov. 8 election, Comey said the FBI had found no additional evidence in the new emails.
John Podesta, who ran the Clinton campaign, said "the report demonstrates beyond doubt" that Comey was unfair to Clinton by announcing developments of the email investigation during the campaign while not revealing the presence of the separate probe beginning in July 2016 into the Trump campaign and Russia.
"This report confirms what we have known for a long time - that the FBI inappropriately applied a double standard to the Clinton and Trump investigations which hurt her and helped elect him," Podesta told Reuters.
The report by Horowitz on the FBI's Clinton probe is due to be released after 2 p.m. (1800 GMT). It arose from a review he launched about a week before President Donald Trump took office in January 2017.
Trump's allies have signalled they will use the Horowitz report to press their argument that Comey did not act properly while overseeing the Russia probe.
The Inspector General also examined whether FBI employees leaked information about investigations of the Clinton Foundation charitable organisation and emails in a bid to help Trump's campaign.
Law enforcement officials previously told Reuters the information was leaked to former New York Mayor Rudy Giuliani, an adviser to the Trump campaign. He now represents Trump in Special Counsel Robert Mueller's probe into whether Russia interfered in the 2016 election.
The report will also discuss Peter Strzok and Lisa Page, two FBI staffers whom Republicans accused of bias against Trump after thousands of text messages sent via their work-issued mobile phones were made public.
While some of their messages were anti-Trump, others took aim at lawmakers such as U.S. Senator Bernie Sanders, whom Clinton defeated for the Democratic presidential nomination.
Page and Strzok were involved in both the Clinton and Russia probes. Mueller removed Strzok from his team after Horowitz disclosed the texts to him.
Comey was fired by Trump in May 2017 while leading the investigation into whether the Trump campaign colluded with Russia, an allegation the president has denied.
(Reporting by Sarah N. Lynch and Mark Hosenball; Editing by John Walcott and Alistair Bell)