Kelly Osbourne has called Dannii Minogue the "devil" and a "poor middle-aged victim" on Twitter.
It comes after Dannii opened up about her feud with Kelly's mum Sharon Osbourne in her new autobiography.
In an extract from Dannii: My Story, the new mum tells the tale of her first night on the X Factor and how Sharon apparently made her cry after screaming and swearing at her minutes before she was due on stage.
Defending of her mum, Kelly tweeted:
"The best thing to happen to Dannii's career was that my mother hated her she needs to shut her mouth and concenterate on motherhood!
"I will be the first one to admit that my mother did not play her cards right when came to Dannii but trust me when I say Dannii is the devil.
She added: "Dannii you are so lucky that I respect Simon enough to not tell the truth about what really happened. wa wa wa you poor middle aged victum (sic)."