Bannon was responding to ABC News Chief White House Correspondent Jonathan Karl after he played video of Trump on the campaign trail in August 2016 telling supporters, "I will never lie to you. I will never tell you something I do not believe... I will always tell you the truth."
"You famously kept a white board of presidential promises to keep track of," Karl said, referring to Bannon's practice when he was at the White House. "That's a promise that [Trump] obviously broke. He has not always told the truth."
Bannon replied, "I don't know that ... From what I see ... he has [told the truth.] This is another thing to demonize him."
Karl pressed, "The president has never lied?"
"Not to my knowledge, no," Bannon said.
Karl cited Trump's false claim Friday that this week's Justice Department Inspector General report on the FBI's handling of the Clinton email investigation "totally exonerated" the president of any collusion or obstruction in the Russia investigation. The report makes no such conclusion.
"He says things that are not true all the time," Karl said.
"I don't believe that," Bannon said. "I think he speaks in a particular vernacular that connects to people in this country."
Some news outlets have made a practice of tracking statements by Trump that are false or erroneous.
On Friday, the president gave an impromptu press conference that was "packed with falsehoods," ABC News reported.
The false claims at the press conference included Trump's repeated assertions that his administration's new policy of separating migrant parents and children who try to cross the U.S. border illegally is due to a law passed by Democrats. There is no law requiring the separation of families trying to cross the border illegally.