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.
Kelly reacted swiftly, calling the report "total BS ".
Kelly, in a statement, said he and Trump have "an incredibly candid and strong relationship".
"This is another pathetic attempt to smear people close to President Trump and distract from the administration's many successes", Kelly stated in his statement.
One source familiar with the situation said Trump was rankled by the way Kelly handled the Porter situation; the chief of staff initially attempted to defend Porter against the allegation until a photograph of Porter's ex-wife's blackened eye surfaced and sparked outrage. That episode created what White House officials described as an irreparable rift between Trump and his chief diplomat, and ultimately led to Tillerson's unceremonious March firing.
Officials: Kelly has "eroded morale" in the White House by making comments disparaging Trump's intelligence and portraying himself as the savior of the nation. "He'll say it and you think, 'That is not what you should be saying'".
Moreover, a number of people whom Kelly ousted or blocked from the West Wing - including Lewandowski and Anthony Scaramucci - are known to frequently fill the president's ears with attacks on the chief of staff while telling Trump that Kelly has been holding him back.
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Rudolph joins a quarterback room that includes Roethlisberger, former Oklahoma Sooner Landry Jones and Josh Dobbs . The Steelers have one of the NFL's top receivers in Antonio Bryant, who had 101 catches for 1,533 yards in 2017.
The report also suggested the chief of staff holds that women are generally more emotional than men, and he said so once in the president's presence.
Fuentes told The Hill that he has "never heard the chief of staff call the president an idiot".
The public revelation of an insult directed at the president's intelligence is reminiscent of leaks previous year that then-Secretary of State Rex Tillerson called Trump a "moron". During the rally, which one person likened to a trial, Trump called Lewandowski on stage and praised him for not being a "pushover" or a "patsy".
Current and former White House officials said Kelly has at times made remarks that have rattled female staffers. The doctor, who said that Trump would be the healthiest individual ever elected as president if he won, is now speaking out and alleging that members of Trump's staff raided his office shortly after Trump's inauguration. But others say it's anyone's guess.
But his relationship with the president has apparently been shaky, and Kelly has reportedly criticized Trump and bashed the president's knowledge on key issues facing the administration.
"Kelly appears to be less engaged, which may be to the president's detriment", a second senior White House official said.
Spokespersons: They haven't heard anything of the sort but did admit that, at times, Trump "gets frustrated" with Kelly for not giving him enough information.