John Kelly, the White House chief of staff, has been forced to deny a report that he called Donald Trump an “idiot”.

In a rapid response statement issued on Monday, Kelly dismissed the claim, broadcast by NBC News, as “total BS”.

The denial was quicker and more direct than that offered by the then secretary of state, Rex Tillerson, when he allegedly described the US president as a “fucking moron” and then ducked questions about it. Trump challenged Tillerson to an IQ test and eventually fired him.

The NBC News report quoted officials as saying Kelly portrays himself as fighting a lonely battle to curb Trump’s erratic impulses and stave off disaster. “He has referred to Trump as ‘an idiot’ multiple times to underscore his point, according to four officials who say they’ve witnessed the comments.”

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Kelly issued a denial via the White House, saying that he and the president have “an incredibly candid and strong relationship”. He added: “He always knows where I stand and he and I both know this story is total BS.”

Kelly insisted that the report “is another pathetic attempt to smear people close to President Trump and distract from the administration’s many successes”.

But NBC News stood by its story. Stephanie Ruhle, a journalist on the network, responded via Twitter: “As one of the people who worked on the story, I can tell you, it is WELL sourced. As for ‘smearing’ the President, those on your team recount stories of you (not us) undermining his credibility.”

According to NBC News, Kelly used the “idiot” term during closed-door meetings with other White House officials while negotiating the Deferred Action for Childhood Arrivals (Daca) programme, which Trump tried to end last year.

“He doesn’t even understand what Daca is. He’s an idiot,” Kelly said in one meeting, two officials who said they were present told the network. “We’ve got to save him from himself.”

The claim is likely to cause fresh speculation about Kelly’s future in the White House. The retired four-star marine corps general was brought in last summer to instill discipline after the chaotic tenure of Reince Priebus. But numerous media reports suggest that he has been marginalised as Trump wearies of being controlled and seeks to cut loose.

A report by the Washington Post, based on interviews with 16 administration officials, outside advisers and presidential confidants, said Kelly no longer listened in on many of the president’s calls, even with foreign leaders, and cast him as “the latest high-profile example of a West Wing Icarus – swept high into Trump’s orbit, only to be singed and cast low”.

Kelly also upset his boss in in January when he said during a Fox News interview that Trump had “evolved” on immigration and said things during the campaign “that may or may not be fully informed”.

Trump appeared to respond to the report on Monday night, renewing his attack on the media in a tweet that said: “The Fake News is going crazy making up false stories and using only unnamed sources (who don’t exist). They are totally unhinged, and the great success of this Administration is making them do and say things that even they can’t believe they are saying. Truly bad people!”

In a second tweet he claimed the White House was “running very smoothly” with “great Energy” and “unending Stamina”. He added: “We are accomplishing the unthinkable and setting positive records while doing so! Fake News is going ‘bonkers!’”

