Stephen Bannon, US President Trump's former chief strategist, says Senator Bob Corker should “resign immediately” if the Tennessee Republican has “any honor or decency,” following his disparaging remarks about the president's ability to lead.

"If Bob Corker had any honor or decency, he should resign immediately," Bannon said in an interview with on Fox News on Monday night.

He added that Corker, Senate Majority Leader Mitch McConnell and “the entire establishment, globalist clique have to go.”

"The American people see: This is what they think about President Trump behind closed doors. He happened to tell the New York Times exactly what he thought. It is totally unacceptable," Bannon said.

Trump’s allies on Monday slammed Corker, who engaged in a heated exchange with Trump on Twitter on Sunday. Later in the day, the senator fired back at the president in an interview with the New York Times, saying Trump is leading the US towards World War III, and that he is treating the presidency like a "reality show."

Bob Corker, the chairman of the Senate Foreign Relations Committee (Photo by AFP)

Bannon said it was "totally unacceptable" for Corker to question the president’s intelligence level when American troops are fighting wars abroad, after the chairman of the Senate Foreign Relations Committee tweeted on Sunday that "the White House has become an adult day care center."

Bannon was sacked as the White House chief strategist in August. After his dismissal, he vowed to "go to war" for the president’s agenda.

The 63-year-old strategist was labeled as a white supremacist as he was formerly the executive chairman of the far-right news outlet Breibart, an online news website which many believe publishes racist articles.

Bannon on Monday pointed out that many other lawmakers in the Republican establishment share Corker’s views about Trump, saying they have "total contempt for the forgotten man and the [Republican] base."

He said he agreed with Jason Miller, Trump's ex-communications strategist, who called for Corker to resign immediately. Corker has announced that he is retiring after 2018.

Former top Donald Trump aide Jason Miller (Photo by Getty Images)

“And look, if Senator Corker is retiring and he doesn't want to be in the U.S. Senate and he doesn't want to support President Trump and doesn’t want to support such basic conservative principles, he should just resign,” Miller told CNN.

A firm supporter of Trump during last year’s presidential election campaign, Corker turned against Trump after being shortlisted for both the vice president and secretary of state.

Corker said Wednesday that Secretary of State Rex Tillerson, Secretary of Defense James Mattis, White House Chief of Staff John Kelly and other top administration officials “help separate us from chaos.”

Earlier on Monday, McConnell defended Corker, calling him "a valuable member of the Senate Republican caucus.”

US Senate Majority Leader Mitch McConnell (R-KY) speaks during a news conference to discuss their plans for tax reform, September 27, 2017 in Washington, DC. (Photo by AFP)

"Sen. Corker is a valuable member of the Senate Republican caucus and he's also on the Budget committee and a particularly important player as we move to the floor on the budget next week and he's an important part of our team," the Kentucky Republican said.