Trump accused Manigault Newman, the former White House liaison to black voters, as "wacky" and "not smart" after his former co-star revealed her recording of a phone conversation with the president during a media blitz for her new book.
"Wacky Omarosa, who got fired 3 times on the Apprentice, now got fired for the last time", Trump tweeted.
"They continue to deceive this nation by how mentally declined he is", she said, referring to Trump, "how hard it is for him to process complex information. She begged me for a job, tears in her eyes, I said Ok", Trump tweeted on Monday.
A spokeswoman for Melania Trump says the first lady is disappointed by the "self-serving way" that former White House aide Omarosa Manigault Newman is "lashing out" and "retaliating" against President Donald Trump.
Omarosa what's going on? "Damn it. I don't love you leaving at all". On the recording aired Monday morning, Trump is heard expressing surprise that Manigault Newman was sacked.
The Associated Press independently listened to the recording of the conversation between Manigault Newman and Kelly, which she said was one of many she'd surreptitiously recorded for her own protection. 'I can't believe someone would even think about doing something like that'.
It appears to show Mr Trump expressing surprise, saying "nobody even told me about it".
He continues: "I didn't know that".
NBC News said it does not know what was heard before or after the exchange between the two.
Guthrie grilled Manigault Newman about Trump during their sit-down on Monday, and the conversation got tense as Manigault Newman replied defensively.
The release of the audio comes one day after Manigault Newman shared a separate recording of what she says is the conversation in which Kelly informed her she was being fired. Omarosa Manigault Newman referred to Melania as an astute student of fashion who purposefully tries to send a message through the outfits she wears, even if the message isn't always clear.
She was harshly criticized by Trump aides and national security experts for the secret recordings saying it was a serious breach of ethics and security.
"Who in their right mind thinks it's appropriate to secretly record the White House chief of staff in the Situation Room?" tweeted Ronna McDaniel, chairwoman of the Republican National Committee.
"The moment I said I would like to leave and they said I can't go, it became false imprisonment", she said.
What does the "Trump tape" say?.
Trump claimed on Twitter that Newman had "fully signed" a non-disclosure agreement, reportedly required of senior Trump White House officials. "And then you can go on without any type of difficulty in the future, relative to your reputation".
In a recording she released of her dismissal, the man assumed to be Mr Kelly speaks of "significant integrity issues" as the reason for firing her, mentioning her use of government vehicles. "I would rarely see her but heard". When we had planning meetings and stuff like that I got along with her.
White House spokesman Sarah Sanders blasted the former staffer after her appearance. Attached to the offer was an agreement that she not make disparaging comments about the president. And she also promised she has more audio recordings and is considering releasing them. The conversation she had with the president, the conversation I had with the president, John Kelly, these are all private, ' he said. You know, they run a big operation, but I didn't know it.