The 26-year-old unleashed a tirade of abuse against the singer after she was asked to comment on her Givenchy dress as part of E!'s Fashion Police.
Host Joan Rivers, 78, said Aguilera looked like she had been 'stuffed into' the LBD, before Osbourne lashed out with, 'Maybe she is just becoming the fat bitch she was born to be. I don't know. She was a c**t to me. And she bought my house!
'She called me fat for so many f***ing years,' Osbourne continued, '…so you know what? F**k you! You're fat too.'
Their feud reportedly started in 2003 when Osbourne said that Aguilera's Christmas CD made her want to 'stab myself'.