AceShowbiz -

Gwyneth Paltrow was messing with the wrong woman when she said she "looked crazy" like Joan Rivers after trying Botox. The 79-year-old "Fashion Police" star criticized the "Iron Man 3" actress back, calling her "skinny" and dropping B-word in the process.

"When I put my head up my a**, I look like her -- which is why I don't do that, either!" Rivers says in a stinging statement to Celebuzz. "Sweetheart, eat a sandwich! Make a hat of white bread and put it on. Take some ketchup and just paint your nails with it. Have a good time, you skinny b***h."

The E! fashion critic didn't stop there. In another response issued to PEOPLE, she said, "First reaction: 'Ooh, she watches Fashion Police!' It just made me laugh. She says Botox made her scary like Joan Rivers? She should see what I look like without Botox. That's really scary!"

"I've always been open about what I do, because I want [women] to be able to get Botox and not look like a Sharpei," Rivers went on. "[Lying about having work done] is such a put down to women. It says to the average woman: 'I'm beautifully naturally and you're not.' "

"I would have written the response myself, but I have so much Botox in my thumbs, I can't type," Rivers quipped. "If she lived in New York, I'd tell her to go to hell." Since Paltrow now lives in London after marrying Coldplay's Chris Martin, Rivers said in a British accent, "Go to Halifax!"