Foxx attacked his Sirius radio network colleague on his Foxxhole show earlier this week, prompting Stern to take aim at the Oscar winner on his program.
The "Ray" star and his crew started the war of words by criticizing Stern and the host's sidekick Robin Quivers for making comments about Sidibe's weight during a show last month.
One of Foxx's co-hosts said Quivers "has a lot in common with 'Precious,' she was overweight, she was once black."
Foxx, himself, then joined in, stating, "I hope that this feud gets us hot, because Howard hasn't really made a big splash in a long time."
His comment enraged Stern, who has fired back, "I'm not... gonna sit here and take it and listen to some bulls**t... I'm going to end it now, because, you know what, I got a s**tload of stuff on Jamie, which isn't a lot of fun.
"Jamie's not a friend of mine. I've had him on the show a couple of times. I don't consider him a friend anymore... I don't dislike the guy, he's a very talented guy."
Stern then poked fun at the name of Foxx's radio show, joking, "I wonder which hole they're referring to."
Last month, Stern said, "She is enormous. Everyone's pretending she's a part of show business and she's never going to be in another movie. She should have gotten the Best Actress award because she's never going to have another shot. What movie is she gonna be in?"
"And Oprah's lying and saying you're going to have a brilliant career," replied Robin, refering to Winfrey's ongoing support of Sidibe..
"Oprah's another liar, a filthy liar," concluded Stern. "She's telling an enormous woman the size of a planet that she's going to have a career."
Whoa! I know they put a segment from the Foxxhole on Twitter last Friday but I was half-listening and wound up turning it off. I had no idea that they were arguing over Gabby. People need to leave that girl alone. She ain't bothering nobody and I'm glad she has a great spirit. Her self-esteem is through the roof, probably more than some of these folks out here clowning her because of her weight. If she was a small build, they'd still find something wrong with her, so she's damned if she do, damned if she don't.