A top investigative journalist who promoted information from the so-called “Trump dossier” that claimed Donald Trump's 2016 presidential campaign colluded with Russia now says the media should have approached the document with "more skepticism.”

“I think it’s fair to say that all of us should have approached this, in retrospect, with more skepticism, particularly when we didn’t know where it was coming from,” Michael Isikoff, chief investigative correspondent for Yahoo News, told Vanity Fair. “We knew that Steele compiled it, but that Steele did not hear these allegations himself. Somebody else heard them from others and then passed them along. That’s thirdhand stuff, which is not usually the kind you want for publishing."

Pictured is Michael Isikoff in 2007. (Wikimedia Commons)

The dossier, composed by former British intelligence officer Christopher Steele, 54, contained scandalous and unverified claims about Trump's connections to Russia and was used by the FBI to obtain a warrant and three renewals to conduct surveillance on Trump campaign aide Carter Page.

By January 2017, FBI agents had reportedly concluded that some of the dossier’s contents may have been based upon “rumors and hearsay” which were “passed from source to source” and perhaps even upon “Russian disinformation.” Watergate journalist Bob Woodward has been calling Steele’s dossier “garbage” for over two years.

It was funded in part by the Democratic National Committee and Hillary Clinton's 2016 campaign through the Perkins Coie law firm and opposition research and business intelligence group Fusion GPS, which had contracted Steele.

Steele met with Isikoff, 66, in September 2016. Also at the meeting was Isikoff’s long-time friend Glenn Simpson, 55, the founder of Fusion GPS. The three discussed Trump and Russia, and Steele provided him with some of his research, but Isikoff has maintained he didn’t know that Fusion GPS was being paid by the Clinton campaign and DNC at the time.

Isikoff wrote an article based in part on his conversations with Steele for Yahoo News. It was later used in the Foreign Intelligence Surveillance Act applications targeting Carter Page. Iskoff said he was stunned when he learned that, saying “it’s self-referential” and “it seems a little odd that they would cite the Yahoo News story about the matter they are investigating themselves based on the same material that had been separately presented to the FBI.”

David Corn, 60, the D.C. bureau chief for Mother Jones magazine, met with Steele in October 2016. An article of his, published just over a week before the November presidential election, quoted various allegations made in the dossier and revealed — without using his name — that Steele had provided his dossier to the FBI to investigate.

Isikoff and Corn co-wrote the 2018 book, Russian Roulette: The Inside Story of Putin's War on America and the Election of Donald Trump, which one reviewer wrote left "the reader nearly overwhelmed by evidence that Trump and Vladimir Putin have been striving to collaborate for years."

In the book, they explained that the dossier made its way into the hands of John Brennan and James Clapper by early 2017. They said a reference to the dossier was even in an early version of the 2017 intelligence assessment on Russian interference, but was then removed.

Steele also worked with one-time Sen. John McCain's aide, David Kramer, who in a recent deposition said he provided BuzzFeed with a copy of the dossier and had spoken with more than a dozen journalists about it. BuzzFeed published the dossier in early 2017.

Justice Department Inspector General Michael Horowitz is now investigating Foreign Intelligence Surveillance Act abuse. Horowitz is reportedly focusing on Steele, but Steele has declined to cooperate with the probe.

Special counsel Robert Mueller’s Russia report, released this month, undercut some of the most scandalous allegations included in the dossier, including that the Russians had obtained compromising information on Trump. Mueller found no evidence to support the accusation in the dossier that Trump watched Russian prostitutes urinating on a Moscow hotel bed while being secretly filmed by the Russians.

“It’s been surprising to me the degree to which some people have wanted to maintain that the dossier was checking out when, as far as I can tell, it hasn’t,” Isikoff said. “There are aspects in there, like cultivating Trump on business relationships, that there is support for, so it’s not a total wash. But it’s the specifics that really knocked people over the head, that really set expectations for what Mueller was gonna find — a vast criminal conspiracy of collusion — and the reality seems to be that the relationships are murkier than that.”

Even so, Isikoff said that Republican’s attacks on Mueller’s investigation are unwarranted. “None of this justifies the Republican jihad to undermine the entire investigation,” he said.

BuzzFeed editor-in-chief Ben Smith, who stood by his decision to publish the dossier in 2017, agreed that “Mueller really did knock down substantive parts of it.”