The Justice Department’s inspector general, in a long-awaited review concerning the origins of the Russia investigation, determined that the FBI complied with policies in launching the politically explosive probe -- but also flagged "significant concerns with how certain aspects of the investigation were conducted and supervised."

Specifically, the report concluded that investigators found no intentional misconduct or political bias surrounding the probe's launch and efforts to seek a controversial Foreign Intelligence Surveillance Act (FISA) warrant to monitor former Trump campaign adviser Carter Page in the early months of the investigation.

READ: DOJ INSPECTOR GENERAL'S FISA REPORT

The same report also faulted the FBI over numerous errors in the application process. The IG probe identified at least 17 "significant inaccuracies and omissions" in the Page applications and said they would launch a new audit into the FISA process. IG Michael Horowitz and his investigators were at times sharply critical of the bureau's handling of the case, including for failing to share information that would have undercut claims in those documents.

In Washington's highly charged political environment -- and coming amid an impeachment fight -- the sprawling, nearly 500-page report offered immediate talking points for both sides. Senate Democratic Leader Chuck Schumer said Monday it demonstrated that the basis for the probe was "valid," while former FBI director James Comey crowed that the early accusations against the bureau were "all lies."

President Trump, meanwhile, called the FBI's conduct "a disgrace" and said it was "far worse than ever thought possible."

White House Press Secretary Stephanie Grisham said in a statement: "The shocking report from the DOJ Inspector General shows an out-of-control FBI under President Obama and former Director Jim Comey."

Former FBI bosses Comey and Andrew McCabe did get a boost, with an IG finding that they did not act with political bias. The report extended a similar finding to the overall surveillance efforts targeting Page and to the Russia case as a whole. The review determined that "the FBI had an authorized purpose" when agents launched the Russia investigation "to obtain information about, or to protect against, a national security threat or federal crime."

Horowitz and his investigators in part probed how the unverified anti-Trump dossier compiled by former British spy Christopher Steele was used to secure the original FISA warrant for Page in October 2016, as well as other decisions at the outset of the FBI’s counterintelligence investigation of Russian election interference and the Trump campaign, known by the name "Crossfire Hurricane."

The report confirmed that information obtained from Steele was instrumental in the FBI's ability to acquire a FISA warrant on Page, while saying the FBI also omitted key information in the course of obtaining renewals.

The report revealed that when the FBI team handling the Russia probe first considered getting a FISA warrant for Page in August 2016, FBI attorneys thought it was a "close call" as to whether they had sufficient cause. The following month, right after the FBI received information from Steele, FBI attorneys gave the investigative team the go-ahead.

"FBI and department officials told us the Steele reporting 'pushed [the FISA proposal] over the line' in terms of establishing probable cause," the report said. FBI leadership then approved of moving forward based on Steele's information, despite "concerns expressed by a department attorney that Steele may have been hired by someone associated with a rival candidate or campaign." His work was backed by the Hillary Clinton campaign and Democratic Party.

US ATTORNEY DURHAM OBJECTS TO IG FINDINGS ON RUSSIA PROBE ORIGINS IN STUNNING STATEMENT

The IG report also faulted the FBI for not sharing within the department information that could have contradicted allegations in the FISA applications: "[T]he Crossfire Hurricane team failed to inform department officials of significant information that was available to the team at the time that the FISA applications were drafted and filed. Much of that information was inconsistent with, or undercut, the assertions contained in the FISA applications that were used to support probable cause and, in some instances, resulted in inaccurate information being included in the applications."

The report, meanwhile, confirmed that the FBI sent confidential sources to record multiple conversations with Page and Trump campaign adviser George Papadopoulos, as well as a high-level Trump campaign official.

The report acknowledged that in August 2016, amid discussions over a FISA warrant, the FBI conducted a “consensually monitored meeting” between Page and a confidential human source “in an attempt to obtain information from Page" about possible links between the Trump campaign and Russia.

“During the operation, which we describe in greater detail below, Page made statements to the [confidential human source] that would have, if true, contradicted the notion that Page was conspiring with Russia,” it said.

But, the report said, they found “no evidence” the FBI made those statements from Page available to the Office of Intelligence or the National Security Division until mid-June 2017.

Horowitz’s team has questioned why the FBI considered Steele a credible source, and why the bureau seemed to use news reports to bolster Steele’s credibility.

The report made clear that FBI policy requires that "agents must ensure that all factual statements in FISA applications are 'scrupulously accurate,'" yet in the application process for the Page warrant, members of the investigative team "failed" to meet that standard, and committed "significant inaccuracies and omissions" in every application.

Those included the failure to share information with the Justice Department obtained by Steele's primary sub-source which cast doubt on Steele's reliability, in addition to the omission of information the FBI learned from another government agency about how Page had assisted them from 2008 to 2013 regarding his previous contacts with Russian intelligence.

An attorney with the FBI Office of the General Counsel was also found to have “altered” information about Page from the other government agency, and as a result gave a misleading impression that Page had not been providing information to that agency.

The report places blame for the inaccuracies on case agents who gave incomplete information to DOJ attorneys, and who "did not follow, or even appear to know, certain basic requirements" of standard procedures. Case agents were not the only ones considered at fault, however, as the report concludes that there was "a failure not just by those who prepared the FISA applications, but also by the managers and supervisors in the Crossfire Hurricane chain of command, including FBI senior officials who were briefed as the investigation progressed."

Another key subject of the report was the role played by DOJ attorney Bruce Ohr, who had known Steele for years and whose wife Nellie Ohr worked for Fusion GPS, the firm that hired Steele to conduct opposition research for the Clinton campaign. In 2016 and 2017, Ohr received information from Steele and Fusion GPS co-founder Glenn Simpson, but he did not tell his supervisors about this, his wife's work for Fusion GPS, or his role in passing information to the FBI until he was confronted about this late in 2017.

The report's release comes as Washington has been consumed with the impeachment inquiry into Trump. The House Judiciary Committee was holding the inquiry’s latest hearing Monday, days after House Speaker Nancy Pelosi said Democrats are moving forward with plans to bring articles of impeachment against the president over his dealings with Ukraine.

But the FISA report is sure to become a political football of its own, alongside the impeachment probe.

"This was an attempted overthrow, and a lot of people were in on it, and they got caught," Trump said Monday. He called Horowitz's investigation "one of our great achievements," and said that the information being obtained through a broader investigation of the Russia probe led by Connecticut U.S. Attorney John Durham was "this information, plus plus plus."

Attorney General Bill Barr said in a statement that the report "makes clear that the FBI launched an intrusive investigation of a U.S. presidential campaign on the thinnest of suspicions that, in my view, were insufficient to justify the steps taken." He added that "in the rush to obtain and maintain FISA surveillance of Trump campaign associates, FBI officials misled the FISA court, omitted critical exculpatory facts from their filings, and suppressed or ignored information negating the reliability of their principal source."

Barr did note that "most of the misconduct" was committed between 2016 and 2017 by former FBI officials, and that he has "full confidence" in current FBI Director Christopher Wray and "the thousands of dedicated line agents who work tirelessly to protect our country."

Durham, meanwhile, stated that he disagrees with some of Horowitz's assessments regarding the beginning of the FBI's case.

"Based on the evidence collected to date, and while our investigation is ongoing, last month we advised the inspector general that we do not agree with some of the report’s conclusions as to predication and how the FBI case was opened," Durham said in a statement, signaling his ongoing probe could be tougher.

Meanwhile, McCabe's attorney Michael R. Bromwich cited Horowitz's report as vindication for his client, who was the FBI's deputy director at the inception of the probe.

"[A]lthough the OIG’s detailed review of the original warrant and the three renewal applications found numerous errors, process failures, and isolated instances of misconduct, the OIG found that those took place at multiple layers below Mr. McCabe and other high-level executives at the FBI and DOJ," Bromwich said, pointing out that the report showed that there was "ample factual basis" for the launching of the Russia probe.

McCabe has been facing the prospect of federal charges after Horowitz faulted him in a separate inquiry over statements he made during a Hillary Clinton-related investigation. The review found that McCabe "lacked candor" when talking with investigators, but the former FBI official has denied wrongdoing. McCabe has not been indicted.

The inspector general has said his team has “reviewed over 1 million records and conducted over 100 interviews, including several witnesses who only recently agreed to be interviewed.” Page, who has been vocal about his belief that he was unjustly targeted, has expressed frustration over not being interviewed for Horowitz’s investigation. Page was never charged with a crime as a result of the surveillance.

Trump and his Republican allies have long questioned the Justice Department’s efforts to secure the surveillance warrants. Earlier this year, Barr said "spying" did occur against the Trump campaign during the campaign. But critics pushed back: Comey, who was FBI director at the time, dismissed Barr’s claims, saying he “never thought of” electronic surveillance as “spying.”

Next, Horowitz is scheduled to testify before the Senate Judiciary Committee Wednesday morning to answer questions about his probe.

CLICK HERE TO GET THE FOX NEWS APP

Ahead of the release, some of the people who worked at the FBI at the time attempted to get ahead of the report to defend their actions. Lisa Page, the ex-FBI lawyer who carried on an extramarital affair with former FBI head of counterintelligence Peter Strzok as the two exchanged anti-Trump text messages during the investigation, recently granted an interview for a sympathetic piece at The Daily Beast, saying “there’s no fathomable way that I have committed any crime at all.”

Fox News' Alex Pappas contributed to this report.