The reality TV star slammed the 'Burlesque' actress' fuller figure as she commented on a photograph of her wearing a tight black dress during a segment on E!'s 'Fashion Police'.
She said: "Maybe she's just becoming the fat b***h she was always born to be. I don't know. She was a **** to me.
"She called me fat for so many f**king years, so you know what? F**k you, you're fat too."
Kelly wasn't the only member of the panel to insult Christina, 30, with Joan Rivers comparing her to 'Jersey Shore' star Snooki, saying: "She looks like Snooki's Scandinavian cousin. It's a pretty dress but she's stuffed into it."
This is not the first time Kelly has lashed out at Christina, previously calling her a "p***y".
She said: "She's a p***y. She has a mouth on her, but she's all talk. She only does it because she always has a security guard around to punch anyone she gets in a fight with.
"[Christina] was like 'Yo girl, artists for artists, yo, why you been talkin' s**t?' I didn't understand a word she was saying. But I stopped saying things about her.
"Then she made out like she had started a fight with me, to make herself look cool. She's like a f**king feather. I could pick her up and chuck her across the room.
"I think it's more the fact that we both like to be b*****s, than me really not liking her.
"She does have a beautiful voice. She just has a bad attitude to everything."