Nicki Minaj claims Mariah Carey is worried about "someone stealing her shine".
The singers are both judges on the new season of talent show American Idol. Last month, Nicki was caught on camera screaming profanities at Mariah after they disagreed during an audition.
In the second part of Nicki's reality show Nicki Minaj: My Truth, the star has claimed Mariah felt insecure about her joining the judging panel and also says she was provoked into losing her temper.
"She's admitted she did not want another female doing the show," Nicki is seen telling Young Money president Mack Maine. "She didn't want someone stealing her shine.
"Twenty minutes before that happened, she egged me on. I just know that I had reached my boiling point... I left and when I came back, it was another jab. Nitpicking nitpicking nitpicking… I had to make it clear that if you do this again, I'm going to do this again."
Nicki also hit out at The View host Barbara Walters in the episode.
The TV presenter waded into the feud by claiming that Mariah had told her Nicki said she would "shoot that b***h".
The Starships singer has vehemently denied she ever threatened to use a gun.
"Am I not good enough for you to get my side because I'm a little black girl that raps?" Nicki fumes in one clip from her show. "If I was J-Lo you would have called J-Lo's camp - so are we not good enough for you? I did not say I was a gangster, I would never say that.
"Then I hear that Mariah went to Barbara Walters with more fabrications which even the producers said I never said. I've never in my life said anything regarding a gun."
Despite their heated exchange, Nicki is still full of praise for Mariah's vocal talents.
She also insists she is enjoying her time on American Idol and will not be intimidated by the other judges.
"I'm happy that Mariah's on the panel. You got one of the best singers who ever sung on the world…" she explained, before referring to their disagreement. "In life, you react, and what you saw was a reaction. Leading up to it, there was a lot of passive aggressive comments. It was another way to get me off the show.
"No-one going to run me off that show."