The Justice Department inspector general report released Monday into the Obama administration's Russia-collusion investigation presents evidence that the FBI misled the Foreign Intelligence Surveillance Court in its effort to obtain a warrant to surveil a Trump campaign adviser.

The FBI's application was filled with errors, omissions and uncorroborated information, according to Inspector General Michael Horowitz's report. And the bureau knowingly withheld exculpatory information, using "defensive briefings" to secretly access the Trump campaign

Attorney General William Barr said the report shows the Obama FBI's application was unjustified.

"The Inspector General's report now 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 said.

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Read the inspector general's report

Significantly, Horowitz concluded the dossier played "a central and essential role in the decision by FBI OGC to support the request for FISA surveillance targeting Carter Page, as well as the FBI’s ultimate decision to seek the FISA order."

The investigators found at least 17 "significant" errors in the applications to surveil Trump campaign adviser Carter Page and said it would launch a new audit into the FISA process.

But they found no intentional misconduct or political bias on the part of key officials, including former FBI Director James Comey and former Deputy Director Andrew McCabe.

Horowitz, however, found that while FBI special agent Peter Strzok was directly involved in the decisions to open the counter-intelligence probe of the Trump campaign, dubbed Crossfire Hurricane, other high-level decision-makers were involved.

Strzok's intent to prevent Trump from winning in 2016 and to provide an "insurance policy" to undermine him if he were to win the White House, was infamously revealed in texts with his FBI lawyer paramour.

The Horowitz investigation centered on how the unverified anti-Trump dossier compiled by former British spy Christopher Steele and funded by the Hillary Clinton campaign and the Democratic National Committee was used as evidence to secure the original warrant for Page. Steele later admitted under oath that his report, based on anonymous Russian sources, was unverified. Special counsel Robert Mueller debunked many of its main claims and was unable to verify any of them.

The inspector general found that the FBI used Steele and his dubious claims to get information on Lt. Gen. Michael Flynn, who is appealing his plea of guilty for lying under oath.

The bureau, according to the report, promised Steele he would be paid "significantly" for his information.

At the White House, President Trump commented on the Horowitz report, saying it's conclusions are "everything a lot of people thought it would be, but far worse."

"It's a disgrace what's happened with respect to the things that were done to our country. It should never happen to another president," he said.

"It's far worse than I ever would have thought possible."

Durham objects

U.S. Attorney John Durham, who is conducting a Justice Department criminal investigation of the origins of the Trump-collusion probe, disagreed with Horowitz how the Obama probe was opened and the basis for it.

"I have the utmost respect for the mission of the Office of Inspector General and the comprehensive work that went into the report prepared by Mr. Horowitz and his staff," Durham said.

"However, our investigation is not limited to developing information from within component parts of the Justice Department. Our investigation has included developing information from other persons and entities, both in the U.S. and outside of the U.S."

Durham said that 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."

Obama FBI targeted 4 in Trump campaign

Rep. Jim Jordan, R-Ohio, pointed out while it previously was believed that the FBI spied on two Americans associated with the Trump campaign, Horowitz found that four individuals were targeted.

"The Inspector General's report confirms what many of us feared: James Comey's FBI ignored guidelines and rules in spying on President Trump’s campaign in 2016," he wrote on Twitter. "We now know that within one week of the investigation opening, the FBI was surveilling the campaign and four specific individuals associated with it."

Jordan said the U.S. government's "powerful tools designed and authorized for international intelligence gathering were deployed to monitor the activities of a Presidential campaign."

"This is a grave matter that should deeply trouble Americans of all political stripes," he said.

Rep. Mark Meadows, R-N.C., noted the report found the FBI "fell far short" in vetting the accuracy of the Obama administration's FISA applications.

"And after reading this, it's no wonder we've been seeing defensive leaks in the New York Times and CNN," Meadows said. "And that the Democrats rushed to hold an impeachment hearing the same day."

Meadows said the report is "every bit as bad as advertised" and "certainly worse than the media has been suggesting."

On his nationally syndicated show Monday, talk-radio host Rush Limbaugh reacted to the finding of no political bias on the part of Obama administration officials.

"Horowitz did not encounter a witness who said so. It doesn't mean that there wasn't, it just means that he couldn't find it, because nobody copped to it," he said.

"All it means is that nobody admitted, and no one provided any witnesses of political bias."

Limbaugh observed that the officials under scrutiny are "circling the wagons," meaning it's unlikely they would "spill the beans on each other."