The long-running feud between singer Christina Aguilera and celebutante Kelly Osbourne is heating up once again. Osbourne took the opportunity to roast the "Beautiful" singer on a recent episode of E!'s Fashion Police. It all started when fellow panel member Joan Rivers skewered a full-figured Aguilera for looking "stuffed into" her little black dress while walking the red carpet at an event in Germany last month. Osbourne wasted no time in going after her archenemy, telling Rivers, "Maybe she is just becoming the fat (witch) she was born to be. I don't know. She was a (expletive) to me. And she bought my house! She called me fat for so many (expletive) years. So you know what? (Forget) you! You're fat too." Osbourne has been battling her weight for years. However in 2009, she dropped a whopping 50 pounds while appearing on Dancing with the Stars. She's since kept it off. When it comes to their feud, it's hardly one-sided. Aguilera has launched her own verbal assaults against Osbourne in the past. At one awards show, she referred to Osbourne, saying, "Oh Lord, I didn't realize it was still Halloween."