Bannon told attendees at the Values Voter Summit, an annual social conservative conference, to keep up the fight against the "imperial" political class.
"It's not my war, this is our war and y'all didn't start it, the establishment started it," Bannon said. He also said, "Right now, it's a season of war against a GOP establishment."
He had told Fox News' Sean Hannity earlier this week
that he was declaring "war" on the Republican establishment.
The Breitbart chief has been looking to unite Republicans behind President Donald Trump. His efforts highlight growing turmoil inside the Republican Party and the conservative movement.
At the summit, Bannon at one point directed his comments directly at McConnell, warning, "Up on Capitol Hill, it's like the Ides of March. They're just looking to find out who is going to be Brutus to your Julius Caesar. We've cut your oxygen off, Mitch."
In the Shakespeare play, Brutus is among the senators who stabs Julius Caesar, the leader of the Roman Empire and his best friend, in the back.
The speech comes as Bannon is recruiting conservative candidates for the 2018 midterm election and forming a donor network to back them in primary races against incumbent Republican senators.
Most notably, Bannon backed former Judge Roy Moore to oust Sen. Luther Strange in an Alabama Republican primary last month.
"The most important thing is an authentic candidate," Bannon said at the summit. "Whether it's Donald Trump or Judge Moore -- this is who you ought to vote for."
Trump endorsed Strange over Moore, who went on to lose the Alabama primary. At the summit, Bannon said Trump's decision was made due to "bad advice."
"The President had some bad information given to him and some bad advice, and folks told him things that weren't so," Bannon said. "I kind of told him what was going to happen down in Alabama and what was going to stand."
Bannon has been openly attacking members of the Republican establishment for what he sees as hindering President Donald Trump's agenda. Another senator he referenced in the speech was Sen. Bob Corker, whom Bannon called at the summit "a real piece of work."
Earlier this week, Bannon called for Corker to resign
after a public feud between Trump and the Tennessee Republican.
"If Bob Corker has any honor, any decency, he should resign immediately," Bannon said in an interview with Hannity on Monday night.