President Donald Trump frequently used the word “nigger” while he was the host of the reality television show “Celebrity Apprentice” and there are tapes that can confirm it, according to a new memoir by one of Trump’s former White House advisers, Omarosa Manigault Newman.

The claims, based on hearsay, are among the more explosive that Manigault Newman makes in the book, “Unhinged.” It was first reported by the British publication The Guardian, which had an early copy.

Manigault Newman said she never heard Trump use the word herself, a point that critics of her credibility are certain to seize on. But she said that by the time she was fired by White House Chief of Staff John F. Kelly, she had come to realize that Trump was a “racist.”

“It had finally sunk in that the person I’d thought I’d known so well for so long was actually a racist,” she said in the memoir. “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.”

Manigault Newman worked with Trump on the show as a first-season contestant, and then was an adviser to his campaign and later in the White House. She was fired in December 2017, after what White House aides said were multiple instances of misconduct, including misuse of a car service and attempting to photograph her wedding on White House grounds.

The White House initially declined to respond to the allegations in her book, which is scheduled to be released next week, although several advisers have privately questioned her credibility and pointed out that she was very upset at being dismissed.

By midday today, Trump ordered the White House to respond.

“Instead of telling the truth about all the good President Trump and his administration are doing to make America safe and prosperous, this book is riddled with lies and false accusations,” the press secretary, Sarah Huckabee Sanders, said in a statement. “It’s sad that a disgruntled former White House employee is trying to profit off these false attacks, and even worse that the media would now give her a platform, after not taking her seriously when she had only positive things to say about the president during her time in the administration.”

In the book, Manigault Newman said that Lara Trump, the wife of Trump’s son Eric — the de facto campaign manager for the next race — called to offer her a $15,000 monthly contract in exchange for her silence on anything negative about the president.

“If you come on board, we can’t have you talking about that stuff,” she writes that Lara Trump said, adding, “Everything is positive, right?” Within a day, Manigault Newman says she received the contract and a nondisclosure agreement preventing her from talking about anything related to the Trump family or Vice President Mike Pence’s family in perpetuity.

“I declined the offer,” she writes. “I was done with Trumpworld.”

Manigault Newman also suggested she now believed that she was pushed out of the White House because she was close to getting hold of the secret tapes revealing Trump using the racist word.

She also wrote that she has been investigating the existence of tapes that prove Trump used the word since late 2016. During the campaign, rumors emerged of “Apprentice” outtakes featuring Trump saying derogatory things about women and minorities.

They were fanned by a former guest on the show, Tom Arnold, an actor. A former producer tweeted that such things existed. Mark Burnett, the producer of the show and a Trump supporter, resisted pressure to release any such footage.

Former campaign aides said that Manigault Newman was involved in efforts then to sort out whether such tapes existed, and that she never claimed knowledge of them at that time.

Still, in the book she writes that she had revealing sources.

“By that point, three sources in three separate conversations had described the contents of this tape,” she said. “They all told me that President Trump hadn’t just dropped a single N-word bomb. He’d said it multiple times throughout the show’s taping during off-camera outtakes, particularly during the first season of ‘The Apprentice.’”

She added, “I would look like the biggest imbecile alive for supporting a man who used that word.”

When she was fired, she said she had a “growing realization that Donald Trump was indeed a racist, a bigot and a misogynist.”

She continued: “My certainty about the N-word tape and his frequent uses of that word were the top of a high mountain of truly appalling things I’d experienced with him, during the last two years in particular.”

Elsewhere in the book, Manigault Newman paints an unflattering portrait of Ivanka Trump, the president’s elder daughter. She describes Ivanka Trump’s involvement in trying to obtain a list of names of people suspected of leaking information about the White House.

The Daily Beast reported earlier this week that Manigault Newman had secretly taped her own discussions with Donald Trump and played them for people.

The book contains some basic factual errors, such as asserting that an aide who worked on the transition into the White House was brought in months later.