Attorney General William Barr doubled down in a new interview Friday on his claims that President Trump’s 2016 campaign was spied on — and vowed to get to the bottom of “exactly what happened” with counterintelligence activities.

In an interview with Fox News that aired Friday, Barr lashed back at Democrats who have rebuked him over his handling of special counsel Robert Mueller’s report.

He also called House Speaker Nancy Pelosi’s claim that he lied to Congress “laughable” as he dismissed an attempt to hold him in contempt of Congress.

“That’s part of the usual … political circus that’s being played out. It doesn’t surprise me,” the nation’s top law enforcement official told host Bill Hemmer during a visit to El Salvador.

Barr forcefully defended his decision to look into the origins of the Russia probe after his appointment of John Durham, the US attorney in Connecticut, to lead the effort because the answers he has gotten so far have been “inadequate.”

“The first step is to find out exactly what happened, and we’re trying to get our arms around that, getting all the relevant information from the various agencies and starting to talk to some of the people that have information,” Barr said on Fox News.

“I think there’s a misconception out there that we know a lot about what happened,” he said. “The fact of the matter is Bob Mueller did not look at the government’s activities. He was looking at whether or not the Trump campaign had conspired with the Russians.

“But he was not going back and looking at the counterintelligence program. And we have a number of investigations underway that touch upon it — the main one being the office of inspector general that’s looking at the FISA warrants.”

Republicans have long speculated that the FISA warrants used to approve government surveillance of Trump campaign foreign policy adviser Carter Page were improperly granted.

Trump first floated the idea he’d been spied on in March 2017, claiming President Barack Obama “had my ‘wires tapped’ in Trump Tower just before the victory,” calling it “McCarthyism!”

In the Fox interview, Barr said “some very strange developments” took place during the period between Election Day and Inauguration Day, including a January 2017 briefing that intelligence officials gave the president at Trump Tower.

“That’s one of the things … we need to look at,” Barr said of the intel meeting in which Trump was briefed on Russian hacking.

The president was informed by then-FBI Director James Comey after the briefing about allegations against him regarding Russian ties in a dossier prepared by former British spy Christopher Steele for an anti-Trump client. Details of the unverified allegations were leaked to the press.

A source told Fox News that the attorney general is working “collaboratively” on the probe with FBI Director Chris Wray, CIA Director Gina Haspel and Director of National Intelligence Dan Coats.

Durham also is working with Justice Department Inspector General Michael Horowitz, who is reviewing alleged misconduct in issuance of FISA warrants, and the role of FBI informants during the early part of the probe, the source told the network.

Barr stressed in his Fox interview that it was of paramount importance “to find out what the government was doing during that period.”

“I’ve been trying to get answers to questions and I found that a lot of the answers have been inadequate. And I’ve also found that some of the explanations I’ve gotten don’t hang together,” Barr said.

“So in a sense, I have more questions today than I did when I first started. Some of what things don’t hang together, some of the explanations of what occurred. People have to find out what the government was doing during that period. If we’re worried about foreign influence, for the very same reason shouldn’t we be worried about whether government officials abused their power and put their thumb on the scale?”

He added: “I’m not saying that happened, but I’m saying that we have to look at that.”

In his comments about Pelosi, Barr said the California Democrat’s claims that he lied under oath were “laughable.”

“I think it’s largely being made to try to discredit me partly because they may be concerned about the outcome of a review of what happened during the election,” he said.

“They may be trying to undermine my credibility, but obviously you can look at the face of my testimony and see on its face that there was nothing inaccurate about it.”

During an April hearing, Rep. Charlie Crist asked the AG if he knew why news outlets reported that members of Mueller’s team were upset with Barr’s four-page summary of their probe into Russian meddling and possible obstruction by Trump.

“No, I don’t,” Barr replied at the time. “I suspect that they wanted more put out.”

But it later emerged that Mueller sent him a letter on March 27 – three days after Barr released a redacted version of the report to Congress — warning that the attorney general’s summary “did not fully capture the context, nature, and substance of this office’s work and conclusions.”