The author of the explosive tell-all book, Fire and Fury: Inside the Trump White House, opened up in a new interview about White House staffers discussing President Trump's mental stability.

Michael Wolff discussed with BBC's Radio 4 on Saturday about what he overheard the president’s aides saying during the time he spent in the West Wing.

"The truth is, over this period that I witnessed, this seven or eight months, they all came to the conclusion gradually at first, then faster and faster, that something was unbelievable amiss here," Wolff explained. "That this was more peculiar than they ever imagined it could be.”

“And at the end, they had to look at Donald Trump and say, 'No, this is a man who can't function in his job as president.' He may have been elected president, but that does not turn him into president," he added.

Wolff further told the BBC that these senior aides also described the president as childish with a need for “immediate gratification.”

Wolff wrote in his book that "100 percent" of people close to Trump with whom he spoke concluded Trump was "incapable of functioning in his job." The release of that excerpt, along with a report earlier this week revealed that lawmakers met with a psychiatrist to question the president’s mental health, sparked a national conversation on the topic.

The White House has pushed back on many of the claims made in the book since it hit store shelves on Friday. The president himself even called the book “really boring and untruthful” while calling the author a “total loser.”