WASHINGTON (Reuters) – Republican infighting over the fate of immigrants brought illegally to the United States as children could be so vitriolic that the party loses control of the U.S. House of Representatives next year, Steve Bannon, a former adviser to President Donald Trump, said in an interview airing on Sunday.

Bannon, whose far-right views on immigration, climate and trade helped shape Trump’s presidential campaign and his first months in office, was fired by the Republican president last month in a push to end factional fights within the White House.

In an interview with the CBS program “60 Minutes,” Bannon predicted Republicans could lose control in the House in the 2018 congressional elections because of a looming battle over what to do about 800,000 immigrants known as “Dreamers.”

Trump said last week he would scrap a program called Deferred Action for Childhood Arrivals, or DACA, that allowed the young immigrants to live and work in America.

Bannon supported ending the program, which had been put in place by Democratic former President Barack Obama.

Trump gave the Republican-controlled Congress six months to come up with an alternative, saying he would “revisit this issue” if lawmakers could not agree.

“I‘m worried about losing the House now because of this,” Bannon told CBS.

“If this goes all the way down to its logical conclusion, in February and March it will be a civil war inside the Republican Party,” he said. “And to me, doing that in the springboard of primary season for 2018 is extremely unwise.”

Republicans are divided over the Dreamers. Some believe they are illegal immigrants who are taking American jobs, while others say they contribute to the country and deserve compassion.

Bannon, who said he left the White House on his own terms, lashed out against “establishment” Republicans who have at times grappled with Trump, a real estate celebrity who had never before held elected office.

“The Republican establishment is trying to nullify the 2016 election,” Bannon said, saying it was an “open secret on Capitol Hill” that many Republicans did not support Trump’s agenda, and singling out Senate Majority Leader Mitch McConnell and House Speaker Paul Ryan for criticism.

“They do not want Donald Trump’s populist, economic nationalist agenda to be implemented,” Bannon said.

He called Republican national security officials who had served in the George W. Bush administration “idiots,” including former secretaries of state Condoleezza Rice and Colin Powell, and former Vice President Dick Cheney.

“I hold these people in contempt, total and complete contempt,” Bannon said, blaming them for U.S. trade problems with China and involvement in Iraq.

“They’re idiots, and they’ve gotten us in this situation, and they question a good man like Donald Trump,” Bannon said.