Kim Zolciak-Biermann and NeNe Leakes' feud is getting more serious as the former has now threatened to sue the latter unless she apologizes for her "racist" comment.

Zolciak-Biermann earlier confirmed that she hired a legal counsel over her feud with Leakes. TMZ has learned that the "Real Housewives of Atlanta" star has sought the help of Allison Hart from the high-powered law firm Lavey & Singer. The lawyer has already made a "super threatening demand letter."

The letter obtained by the publication references to Leakes' comments on social media. "Kim & her child did something very wrong & disgusting! Black people and roaches in the same sentence don't work for me boo. Kim & her daughter oops whole family are racists!" the document quoted Leakes. Zolciak-Biermann also included Leakes' hashtags "#racisttrash" and "#KKK."

In the letter, Zolciak-Biermann also called Leakes' statements "outrageous and malicious lies." In addition, her attorney stated that Brielle Biermann never posted the video with cockroaches crawling on the floor and that it was Leakes who shared it on Twitter and Instagram.

Zolciak-Biermann also claimed that Leakes was going after her and her daughter because she was jealous of them as they have a successful show, "Don't Be Tardy," on Bravo. The former "Dancing with the Stars" participant also added that the "Glee" alum tried to encourage her followers to boycott their show with hashtags like #blackpeopleneedtostopsupportingtheprejudice.

Attorney Hart wanted Leakes to retract her statements against Zolciak-Biermann and her daughter on social media and issue an apology. If she refuses to do so, Leakes' actions "exposes [her] to multi-million dollar liability," according to the lawyer.

On Tuesday, Zolciak-Biermann appeared on "Larry King Now" and said that she took offense to Leakes' comment about her daughter being racist. "It's inappropriate. In this day and age, people are dying over racism, " she said. "I'm on a show with all African-American women and I'm the only one that's ever been on the show that's Caucasian, so it's the card that sometimes they play and it's gross. And I won't allow it."

The reality stars haven't talked face-to-face after their feud on social media began. And it seems this might continue for a while as Zolciak-Biermann said she has no plans to film and work with Leakes ever again.

Meanwhile, their "RHOA" co-stars have been taking sides in their beef. Porsha Williams seemed to show support for Zolciak-Biermann when she promoted the premiere of the latter's "Don't Be Tardy." On the other hand, Kenya Moore proved she had Leakes' back when she shared the former's post on Instagram and added the hashtags "#sheisabadperson" and "#likemotherlikedaughter," which seem to refer to Biermann. Leakes' controversial post has since been deleted.

Will Leakes apologize to Zolciak-Biermann? Drop a comment below.