Stephen K. Bannon, US President Donald Trump's Chief White House strategist has said the media should "keep its mouth shut".

Bannon laced into the American press during an interview on Wednesday evening, arguing that news organisations had been "humiliated" by an election outcome few anticipated, and repeatedly describing the media as "the opposition party" of the current administration, The New York Times reported on Thursday.

"The media should be embarrassed and humiliated and keep its mouth shut and just listen for a while," Mr. Bannon said during a telephone call.

"I want you to quote this," Bannon added. "The media here is the opposition party. They don't understand this country. They still do not understand why Donald Trump is the president of the US."

The scathing assessment - delivered by one of Trump's most trusted and influential advisers, in the first days of his presidency - comes at a moment of high tension between the news media and the administration, with skirmishes over the size of Trump's inaugural crowd and the president's false claims that millions of illegal votes by undocumented immigrants swayed the popular vote against him.

Bannon, who rarely grants interviews to journalists outside of Breitbart News, the provocative right-wing website he ran until last August, was echoing comments by Trump this weekend, when the president said he was in "a running war" with the media and called journalists "among the most dishonest people on earth".

During a call to discuss Sean M. Spicer, the president's press secretary, Bannon ratcheted up the criticism, offering a broad indictment of the news media as biased against Trump and out of touch with the American public. 

That's an argument familiar to readers of Breitbart and followers of Trump-friendly personalities like Sean Hannity.

"The elite media got it dead wrong, 100 per cent dead wrong," Bannon said of the election, calling it "a humiliating defeat that they will never wash away, that will always be there".

"The mainstream media has not fired or terminated anyone associated with following our campaign," Bannon said. "Look at the Twitter feeds of those people: they were outright activists of the Clinton campaign." 

He did not name specific reporters or editors.

"That's why you have no power," Bannon said, adding: "You were humiliated."

Of all of Trump's advisers in the White House, Bannon is the one tasked with implementing the nationalist vision that the president channeled during the later months of the campaign, one that stemmed from Bannon himself.