Donald Trump has been labelled the "most insecure person that you could ever meet" who wants to run the presidency "like a one-man" Broadway play, by his former communications director.
Anthony Scaramucci, who served under the US leader for just 11 days during July 2017 - said Trump can't "handle conversations intellectually with experts" and called on the American people to vote for Joe Biden.
Appearing on BBC's Question Time, the financier and life-long Republican said he was initially blinded against his better judgement when accepting a role in Trump's inner circle by his fierce desire to work at the White House.
"He may not have changed, but I've changed," he said on Thursday's episode of the political panel show.
"I've become way more psychologically-minded, way more empathetic to what is actually going on and what the struggle is right now."
He said, despite openly supporting the President for two years after he was sacked, Trump's actions - including separating migrant families and "using racist nativist tropes against American Congresswomen" - had made it "impossible" to support him anymore.
Mr Scaramucci was asked by host Fiona Bruce what is driving Trump's response to the coronavirus pandemic, including ordering Americans to shun lockdowns.
"It's personality, he's the most insecure person that you could ever meet in your life, Fiona," he said. "So, he's reflexively contrary."
He went on to say, the President can have the likes of Secretary of Defense Jim Mattis or infectious disease expert Anthony Fauci "in front of him, telling him what to do and he'll do the opposite".
"He's insecure about having experts making him feel inferior and so he's classically mis-handling things.
"I think that's one of the more startling things about him, when you think about his achievements," continued Mr Scaramucci, speaking via video link from the US.
"He ascended to the American presidency but yet he's not somebody that can handle conversations intellectually with experts.
"He wants to run the American presidency as a one-man West End or Broadway play, it's nonsensical."
He said Trump's politicisation of the pandemic has caused a "great frustration" in his country, which can only be put right by voting for Biden - though he admitted he doesn't agree with everything the Democrat stands for.
Referring to Trump, he said: "He's lied to people about the science and he's right now, as we're speaking, flying around the battleground states, creating super-spreader events. I mean, who does this? We're talking about leadership."
The President has consistently touted his ability to draw huge crowds to his campaign rallies in the lead up to election on November 3.
But has come in for criticism, due to the lack of social distancing and face masks on show at such events.
Speaking of America and Britain, Mr Scaramucci said: "One of the things both countries need right now is direct points of honesty and stop shading things, stop spinning things, just say 'look, here are the facts' - this is what we have to do as a country, we want to make ourselves less sick.
"The President of the United States has made our country sicker, weaker and poorer.
"I can't speak for the British Prime Minister...we've got to cut it out," he added.