Sen. Rand Paul (R-Ky.) said Wednesday that former CIA Director John Brennan — who served under former President Barack Obama — was responsible for trying to legitimize the uncorroborated Steele dossier against then-candidate Donald Trump in 2016 by pushing for its inclusion in intelligence assessments.

The senator is now calling for Congress to investigate what "President Obama knew and when."

What are the details?

In a Wednesday tweet, Paul announced that "a high-level source" informed him "it was Brennan who insisted that the unverified and fake Steele dossier be included in the Intelligence Report...Brennan should be asked to testify under oath in Congress ASAP."

According to the Washington Examiner, "at least two other top intelligence officials" have also claimed Brennan included the "salacious" dossier in 2016 intelligence reports. Washington Post journalist Bob Woodward wrote in his book "Fear" that Brennan told him the Steele dossier "was in line" with the CIA's "own sources," Salon reported.

Brennan has been an outspoken critic of President Donald Trump, calling him "treasonous" among other things, but he has denied having a role in promoting the dossier.

Speaking to Fox News Thursday, Paul suggested otherwise and said Brennan didn't act alone.

"My source tells me that the intelligence community — Obama's intelligence community, Brennan, [former Director of National Intelligence James] Clapper, [former FBI Director James] Comey — they were frustrated because they had this Russian dossier but nobody believed it was real, it wasn't verifiable," Paul said. " They couldn't get anything out of it, so they sent spies into the Trump campaign, they tried to entrap Trump officials to admit they were working with Russia, that wasn't working.

"So, they were frustrated," Paul continued, "but they wanted to somehow get this information out — this Russian dossier that even the media wasn't publishing. Nobody would publish it because it was so scandalous, unverifiable, and likely, fiction."

Paul went on to explain, "Finally they decided, 'Well what we have to do is attach this dossier, this fake dossier, to an intelligence report.' So the president receives these intelligence reports, and they're given directly to the president.

"Well, what they do is, they staple to the report this Russian dossier. So now Obama is officially seeing it, and then also it's given to Trump at this point. But realize this is a big circle; they'd had the dossier for months and months. So when John McCain is given the dossier, it's given to him by people who may have leaked it from our government to John McCain, so John McCain can give it back to the FBI," the senator laughed. "I mean, it's a crazy circle, all trying to justify something that wasn't true."

Sen. Paul added, "But extraordinary power of these people and extraordinary corruption .... They tried to bring down a sitting president."

The Kentucky senator has been pushing for a full investigation of the claims against Obama administration officials after last week's conclusion of a two-year investigation by special counsel Robert Mueller, which determined there was no collusion between the Trump campaign and Russia — in spite of what Brennan and others asserted.

"What did President Obama know and when?" Paul asked on Twitter. "How did this hoax go on for so long unabated?"

Anything else?

Sen. Paul has suggested withholding the release of the special counsel's long-awaited report as leverage, in exchange for information on how the investigation was launched in the first place.

"My plan is to object to the release of the Mueller report and/or all of the Mueller information until they also release the complete information from the White House, DOJ, FBI, on why they chose to credit the dossier," he tweeted.