Former White House adviser Omarosa Manigault Newman claims in her new book that President Donald Trump said the Boy Scouts need to "man up" and "grow some hair on their chests" after backlash mounted over his controversial speech.

Speaking at the 2017 National Boy Scout Jamboree, Manigault Newman wrote that she had to tell Trump to be mindful of his audience after he "decided to ramble on" about "fake news," "the swamp," and a "sexist and lascivious" story about a wealthy real estate developer.

His bizarre comments earned widespread backlash, which Manigault Newman wrote made Trump "furious."

The White House has said her book is "riddled with lies and false accusations."

Former White House adviser Omarosa Manigault Newman claims in her new book, "Unhinged," that Trump said the Boy Scouts need to "man up" and "grow some hair on their chests" after backlash over a bizarre speech he gave at their Jamboree last year.

Speaking to the mostly teenage crowd at the 2017 National Boy Scout Jamboree in July, Trump delivered a raucous speech that included mentions of a party attended by "the hottest people in New York", and a story about wealthy real-estate developer William Levitt, whose hard work Trump said allowed him to buy a yacht and lead a "very interesting life."

Manigault Newman wrote in her book that Trump's mention of Levitt's "yacht, [which] was a WWII-era version of the Playboy Mansion. Nudge, wink," came off as "sexist and lascivious," a devolution from when Trump began the story to speak about merits of hard work.

She says she encouraged Trump to be mindful about what is appropriate for his audience, and that he said "[The Scouts] are going to have to man up and grow some hair on their chests. They're not little boys. They have to man up!"

President Donald Trump speaks to a crowd of 40,000 Boy Scouts and their families in West Virginia on July 24, 2017. White House/Andrea Hanks

"Tonight, we put aside all of the policy fights in Washington, DC, you've been hearing with the fake news and all of that. We're going to put that aside," Trump said during the speech. "I said, 'Who the hell wants to speak about politics when I'm in front of the Boy Scouts.'"

But the speech was filled with "political rhetoric". Trump also took shots at former President Barack Obama and his Democratic opponent Hillary Clinton, bragged about his crowd sizes, and assured the Boy Scouts, "Under the Trump administration, you'll be saying 'Merry Christmas' again when you go shopping."

After the speech, the Boy Scouts released a statement distancing the organization from Trump amid criticism from parents.

Manigault Newman wrote that Trump was confused and angered by the criticism, as he "thought he'd done a fabulous job with that speech and was furious about the criticism of it in general, and, specifically, that anecdote" about Levitt's yacht.

President DonaldTrump, front left, gestures as former boys scouts, Interior Secretary Ryan Zinke, left, Energy Secretary Rick Perry, watch at the 2017 National Boy Scout Jamboree at the Summit in Glen Jean,W. Va., Monday, July 24, 2017. Steve Helber/AP

Trump has defended this speech before, as The Wall Street Journal and Politico reported last summer he grew upset at the suggestion it got a "mixed" reception.

"There was no mix there," Trump reportedly said. "That was a standing ovation from the time I walked out to the time I left, and for five minutes after I had already gone. There was no mix."

Several Trump administration officials have hit back at the claims Manigault Newman makes in her book. The White House didn't immediately respond to Business Insider's request for comment on this story.

White House press secretary Sarah Sanders released a statement Friday saying the book is is "riddled with lies and false accusations", and Trump has been attacking Manigault Newman's credibility on Twitter for days.

During the White House press briefing on Tuesday, Sanders said Manigault Newman "clearly cares more about herself than our country."

"She worked here for a year, and didn't have any of these things to say. In fact, everything she said was quite the opposite — not just in the year that she worked here but the time that she spent on the campaign trail," Sanders said "I think it's really sad what she's doing at this point."

"Unhinged: An Insider's Account of the Trump White House" is on sale Tuesday.