Nicki Minaj threatens to 'knock out' Mariah Carey

Nicki Minaj reportedly threatened to punch fellow American Idol judge Mariah Carey. Photo / AP

Nicki Minaj swore and threatened to punch fellow judge Mariah Carey during recent American Idol auditions, reports say.

Show bosses cancelled filming in Charlotte, North Carolina for the day after a huge blow up between the Starships singer and Carey, where Minaj fumed she was sick of her co-star's "f***ing highness" and their fellow panelists Keith Urban and Randy Jackson were caught in the middle.

A source told TMZ: "[Nicki said to Mariah] 'I'm gonna knock you out'.

"Nicki added, 'I told them, I'm not f***ing putting up with her f***ing highness over there."

Producers are worried about how the pair will manage to work together for the rest of the season.

Carey was said to be unhappy with Minaj joining American Idol because she was worried it would turn the reality TV programme into a "freak show".

A source previously said: "Nicki isn't established enough to qualify as a judge.

"Mariah wants a panel of bright, inspirational and constructive judges. Not some freak show! Mariah thinks Nicki will just be a distraction and it will all be about her and her outrageous behaviour.

"Mariah will not be happy if Nicki joins the panel and she has let the producers know just how she feels!"

- Bang! Showbiz