GOP leaders are trying to block Trump's populist agenda, Steve Bannon says Trump 's former adviser was blunt in his first TV interview.

 -- Steve Bannon, President Donald Trump's former chief strategist, did not hold back from criticizing the Republican establishment in his first television interview.

Bannon, who has returned to his website, Breitbart News, was viewed as an outsider who helped shape Trump's populist agenda, and he famously feuded with the more moderate members of the administration as well as the Republican leadership in Congress.

He took aim at Senate Majority Leader Mitch McConnell and House Speaker Paul Ryan.

"They do not want Donald Trump's populist, economic nationalist agenda to be implemented. It's very obvious," Bannon said in an interview with "60 Minutes" that aired on Sunday.

According to Bannon, McConnell asked Trump to stop using "drain the swamp" — one of his campaign mantras — on Day One of his presidency.

Bannon said he plans to go to war with the establishment in Washington.

"The swamp is a business model," he said. "The permanent political class, as represented by both parties ... you're not going to drain that in eight months. You're not going to drain it in two terms. This is going to take 10, 15, 20 years of relentlessly going after it."

Bannon also said he'll keep fighting for Trump and his agenda. After Trump's comments about the violence in Charlottesville, Virginia, caused a firestorm, Bannon pointed out that he was the only one who defended the president. When pushed by interviewer Charlie Rose why Trump did not immediately denounce neo-Nazis and white nationalists, Bannon doubled down.

"What he was trying to say is that people that support the monument staying there peacefully and people that oppose that, that's the normal course of First Amendment," said Bannon.

He continued, "When he's talking about the neo-Nazis and neo-Confederates and the Klan, who, by the way, are absolutely awful — there's no room in American politics for that. There's no room in American society for that ... My problem — and I told [chief of staff John] Kelly this — when you side with a man, you side with him. I was proud to come out and try to defend President Trump in the media that day."

Bannon pointed a finger at members of the administration and early campaign supporters who he said weren't loyal when the cards were down. People's reaction to Trump's infamous 2005 "Access Hollywood" comments came to be a "litmus test," according to Bannon.

He also went after George W. Bush's former team for criticizing the Trump administration's national security policies.

"The same geniuses that got us into Iraq, that's the geniuses of the Bush administration. I hold these people in contempt, total and complete contempt," said Bannon. "You know, the Condi Rice, the George W. Bush, his entire national security apparatus."

Bannon shrugged off the media's criticisms of him, including the "grim reaper" image of him on "Saturday Night Live."

"I don't need the affirmation of the mainstream media. I don't care what they say. They can call me an anti-Semite. They can call me racist. They call me nativist. You can call me anything you want, OK? As long as we're driving this agenda for the working men and women of this country, I'm happy," he said.