Transcript for Omarosa says Trump trying to 'silence' her as campaign files arbitration against her
I had heard -- Since publication of this book? Absolutely. You know it exists? I know it exists. Reporter: The feud between president trump and fmer white house adviser omarosa manigault-newman exploding. On a press tour for her new book, omarosa alleging there is a tape of the president using the "N" word. He is truly a racist. Reporter: A serious departure from what she told our Deborah Roberts last year. Do you think this president is racist? Absolutely not. I would never sit nor work for someone who I believe to be a racist. Reporter: Now president trump's campaign wants to take her to court. They were encouraging the president to not engage on this, don't tweet. Of course that's the first sign we know for the. The to jump right? Reporter: The president launching a vicious counterattack, calling his former adviser a crazed crying lowlife, adding good work by general Kelly for quickly firing that dog. Regardless of what you think about omarosa, regardless what you think about Donald Trump, this is a question of what is outside the boundaries of civil and respectful speech, it's about what becomes miss stodgeny and racist. Is this any way for the president to talk about any American, let alone somebody he hired and made the highest ranking African-American woman in his white house? I think the president is certainly voicing his frustration with the fact that this person has shown a complete hack of integrity. Why did he hire somebody he's describing as a dog, a lowlife? The president wanted to give her a chance. Reporter: In interviews omarosa revealing her secret recordings from inside the white house and the campaign. First to NBC. Omarosa, what's going on? I just saw on the news that you're thinking about leaving. What happened? Reporter: Just yesterday releasing what she claims to be the president calling her the day after she was fired. General Kelly came to me and said that you guys wanted me to leave. No, nobody even told me about it. Wow. Reporter: And this, allegedly the moment she was let go by general Kelly inside the situation room. We've got to talk to you about leaving the white house. There are pretty significant legal issues that we hope don develop into something that will make it ugly for you. Is the president aware of what's going on? Let's not go down that road, this is a nonnegotiable discussion. Any time somebody is violating the trust of the Wiest wing, especially bringing a recording device into those secret room, that is a huge violation of trust. Reporter: Omarosa's new book "Unhinged" full of shocking allegations, in many ways a vicious swipe at the president and administration she used to work for. A total 180. I say Donald, you say Donald! It's hard to be sympathetic given the statements she's made, her percent defense of Donald Trump against all evidence to the contrary. Reporter: The book is filled with alleged bombshells, the most serious being a recording she says from an outtake of "The apprentice" where the president allegedly uses the "N" word as proof the tape exists she cites renowned pollster frank luntz. I'm in the center of a scandal whether or not the president used the "N" word. Reporter: He says he was never contacted by omarosa and it's a complete lie. I still can't understand why she didn't call or text or e-mail. It's part of what's wrong. The people are free to make any accusations without any kind of evidence whatsoever. Reporter: This morning omarosa releasing this recording to CBS. She says it's campaign aides, all who are African-American, seeming to discuss whether the president had been caught on tape using the "N" word. I'm trying to find out at least the context it was used in. To help us maybe try to figure out a way to spin it. Reporter: Another aide says she asked the president about it. I said, well, sir, can you think of any time that this might have happened? And he said no. Well, that's not true, so -- He goes, how do you think I should handle it? And I told him exactly what you just said, omarosa, well, it depends on what scenario you're talking about. And he said, well, why don't you just go ahead and put it to bed? He said it. He said it, he's embarrassed. Reporter: Omarosa delving into the president's marriage, writing she believes the first lady is counting every minute until he is out of office and she can divorce him. In a statement the first lady said she rarely interacted with manigault-newman, adding it's disappointing she's lashing out in such a self-serving way. Omarosa's loyalty is to herself. It beloves her to write a salacious book like this because she is fueled by the attention. Reporter: It's the latest chapter in her long, complicated history with Donald Trump. Once portrayed as the villain on his reality TV show "The apprentice" -- she's called trump a friend ever since he first fired her in 2004. Omarosa has to go. You're fired. Reporter: Thrust into the national spot light, then to the trump campaign. Every critic, every detractor, will have to bow down to president trump. Reporter: She parlayed that success into a job with her old boss, becoming the white house director of communications for the office of public liaison, one of the highest-paid white house staffers, bringing in nearly $180,000 a year. The public spat between former boss and one-time apprentice fallology the one-year anniversary of the violence in charlottesville. Trump's response at the time a notable low point of his presidency. Very fine people on both sides. Reporter: This time the president denounced hate groups in advance of last weekend's unite the right rally in Washington, D.C. The rally fell flat this year. But while the streets outside the white house this weekend may have reflected an intolerance of racism, the optics inside the white house are raising questions on the president's commitment to diversity. Who is the most prominent, high-level adviser to the president on this west wing staff right now? African-American? Yes. I would say that -- well, first of all, you're totally not covering the fact that our secretary of housing and urban development and world-renowned -- I'm asking you about the white house staff. I'm asking about the people the president is working with every day. Well, that's important -- Reporter: Omarosa one of the prominent African-Americans who supported trump. My colleague Dan Harris spoke to omarosa after then candidate trump became the GOP nominee. When you hear Donald Trump referred to as a racist which happens not infrequently, what's your response? You know him. Because I don't just know him through headlines, I know Donald Trump's heart, I know him as a person. I have to acknowledge he is racial. Let me let you know what that means. When he talks about illegal immigrants and they're coming from different countries, that triggers racial reactions from people. Because he's talking about racial incidents. But that does not make him a racist. Reporter: Omarosa now claims she had a blind spot when it came to the president and says she was complicit when he delivered racially insensitive remarks and regrets sticking by him. In some ways Donald Trump has muddied the water of our racial discourse in America. But in other ways he's actually at least allowed for her honest and transparent conversation. Reporter: For "Nightline" I'm Tom llamas, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.