She alleges that, during the making of USA version of The Apprentice, which Trump fronted for several years, the future president muttered the racial slur "multiple times".
Manigault starred in NBC's reality show The Apprentice while it was hosted by Trump.
She also claims without evidence that tapes exist of the president using the N-word repeatedly on the reality show's set.
She also claims to have personally witnessed the president use racial epithets including "Flip" and "goo-goo" to describe White House advisor Kellyanne Conway's husband, George Conway, who is half Filipino.
The New York Times reported that "The White House initially declined to respond to the allegations in her book", but "By midday Friday, Mr. Trump ordered the White House to respond". "Using the N-word was not just the way he talks but, more disturbing, it was how he thought of me and African Americans as a whole". After Omarosa's reportedly dramatic firing in December, Politico reported that chief of staff John Kelly let her go because she was allegedly abusing White House vehicle service privileges, among other infractions. That was in November; by December, Manigault Newman was out of the Trump fold.More news: Death toll rises to 131 in Indonesian quake
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Manigault Newman writes in "Unhinged: An Insider Account of the Trump White House" that she turned down the proposal, which would have barred her from the public criticism she has leveled at Trump since her departure.
Elaborating on her claims over the offensive recording, Omarosa echoes things said by former Celebrity Apprentice contestant Tom Arnold.
Omarosa was sacked in December, when Trump tweeted, "Thank you Omarosa for your service!"
In early 2017, Manigault Newman says she walked Michael Cohen, then Trump's personal lawyer, into the Oval Office for a meeting with Trump - and saw the president chewing up a piece of paper while Cohen was leaving the office.
White House press secretary Sarah Huckabee Sanders speaks during the daily press briefing at the White House, Tuesday, May 1, 2018, in Washington.
NPR's Rachel Martin pointed out the discrepancy to Manigault during the interview, prompting Manigault to try to tell Martin that she hadn't read the book. "He hated him. He never explained why, but now I believe it was because Obama was black".