WASHINGTON (Reuters) - U.S. President Donald Trump on Tuesday called former White House aide Omarosa Manigault Newman a “dog,” and his campaign took legal action against her as the two former reality TV stars escalated their public feud.

Former U.S. White House staffer Omarosa Manigault-Newman gestures during an interview on the release of her book "Unhinged" in Manhattan, New York, U.S., August 14, 2018. REUTERS/Shannon Stapleton

The intensifying spat came as Manigault Newman, a former contestant on Trump’s reality show “The Apprentice,” publicly released more recordings from her time in his orbit as she promoted her tell-all book, “Unhinged,” which describes her year at the White House. She was fired last December.

“When you give a crazed, crying lowlife a break, and give her a job at the White House, I guess it just didn’t work out. Good work by General (John) Kelly for quickly firing that dog!,” Trump wrote on Twitter, referring to his chief of staff.

In her book, Manigault Newman accuses Trump of making derogatory statements about African-Americans, Filipinos and other minorities, as well as exhibiting “forgetfulness and frustration.”

“His mental decline could not be denied,” wrote Manigault Newman, who had been one of the Republican president’s most prominent black supporters.

White House spokeswoman Sarah Sanders, asked if she was surprised by Manigault Newman’s animus toward the president, told reporters she was disappointed by what she called the former aide’s self-serving and false claims.

“I think it’s really sad what’s she’s doing,” Sanders told a White House briefing.

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In recent days, Manigault Newman has released audio of her firing by Kelly and of a call from Trump in which he says he did not know about her dismissal.

On Tuesday, CBS News released another recording it said was unverified but appeared to be Manigault Newman and several Trump campaign aides in October 2016 discussing the potential fallout from a tape of Trump using a racial epithet during the taping of “The Apprentice.”

CBS News' parent company, CBS Corp CBS.N, owns Simon and Schuster Inc, which published her book. In it, Manigault Newman describes the recorded conversation as being a conference call held on Oct. 11, 2016. Reuters could not verify any of the recordings.

Trump on Monday denied the existence of any tape from “The Apprentice” in which he used the racial epithet.

Asked whether she could guarantee such a recording would never surface, Sanders said: “I can’t guarantee anything, but I can tell you that the president addressed this question directly.”

In a related development, a Trump campaign official said the campaign, which is gearing up for his 2020 re-election run, had filed an arbitration against Manigault Newman for breaching a 2016 confidentiality agreement. Asked about the pact, Manigault Newman told MSNBC she did not believe she had violated it.

Critics condemned Trump’s tweet for what they said were racial and sexist undertones.

“The president of the United States is calling a woman of color a dog? ... How dare he call anyone a dog?” Democratic U.S. Representative Frederica Wilson, who is also an African-American, told CNN.

U.S. Senator Jeff Flake, a frequent Trump critic, called the president’s language “unbecoming” and, in a tweet quoting the president’s post, wrote that fellow Republicans “should not be okay with it.”

Trump brought on Manigault Newman, previously known for repeatedly being fired on NBC’s “The Apprentice,” as director of communications for the White House Office of Public Liaison.