Hell hath no fury like Kelly Osbourne, period.
The daughter of rocker Ozzy - and current E! correspondent - used her newfound critic's powers to slam the singer's shockingly plump figure on E!'s "Fashion Police" Friday.
"She called me fat for years," Osbourne, 26, said. "I was never that fat."
Aguilera, 30, stunned fans when she donned a tight black leotard and fishnet stockings at the Michael Jackson Tribute concert the previous weekend, cavorting about stage with messy hair extensions and heavy-handed makeup.
Fellow "Fashion Police" correspondent Joan Rivers backed Osbourne up with a few choice comments of her own.
"Lady Marmalade got into the peanut butter again," the veteran comedian said.
George Kotsiopoulos, a third host on the show, attempted to assuage the situation by pointing out that it was the getup itself that proved unflattering.
"I'm looking at this and thinking, 'Well, she's put on weight. This just isn't flattering'" he said on the show. "But this is just a crappy outfit, regardless. No matter what shape your body is in, it's just bad."
Kotsiopoulos then pointed out that Aguilera was "still probably a size 2/4," to which Osbourne quickly disagreed.
"Trust me, I'm a 2/4," she said. "That is not a 2/4."
Osbourne has attacked Aguilera's figure before, citing past quips the singer has made at her as grounds for her grudge.
"She called me fat for so many f--king years," Osbourne proclaimed on the show last month. "so you know what? F--k you! You're fat too."
#IMJUSTSAYIN A MINUTE AGO SHE LOOKED LIKE MISS PIGGY! E! SHOULD FIRE HER!