She alleges that, during the making of US version of The Apprentice, which Trump fronted for several years, the future president muttered the racial slur “multiple times”.
In his first comments on the matter made during as he met with supporters from a group called “Bikers for Trump” at Trump National Golf Club in Bedminster.
He first took the opportunity to have a dig at the media at the room asking “does everybody like the press?” which was met with a chorus of booing.
A reporter then asked him: “Do you feel betrayed by Omarosa, sir?”
Trump, feigning covering his mouth, answered: “Lowlife. She’s a lowlife.”
He did not address any of the allegations Omarosa has made.
Reports have been circulating for years that outtakes from the reality television show exist in which Trump can be heard saying the N-word.
Manigault Newman does not specify in her book, which is due to be released on Tuesday, whether she heard Trump using the slur or whether she saw footage of him using it.
She claims she also personally witnessed Trump using racial epithets when referencing his aide Kellyanne Conway’s husband George, who is half-Filipino.
“It had finally sunk in that the person I’d thought I’d known so well for so long was actually a racist,” she wrote, according to The Guardian.
“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.”
In the book, Manigault Newman, who was a contestant on Mr Trump’s The Apprentice reality show and later served as a senior adviser to the president, hurls a litany of allegations, painting the president as scattered, self-absorbed, misogynistic and insecure.
She also claims she saw him behaving “like a dog off the leash” at numerous events he attended without his wife, First Lady Melania Trump.
The accusations are among a long list of scandalous claims contained in her new book Unhinged, set to come out on August 14.
The White House has already slammed the book as “riddled with lies and false accusations”.