Skrillex has accused former mentor Deadmau5 of "bullying" him.
The EDM stars have become embroiled in a nasty Twitter spat after Deadmau5 panned the new single from Jack Ü - a production duo featuring Skrillex and Diplo.
Describing the single 'I Need Ü' which features Justin Bieber, Deadmau5 tweeted: "what the f**k is this s**t? (sic)".
But the 'Bangarang' hitmaker took offence to the comment and lashed out at him in a series of tweets, branding him the "worst label head ever".
He responded: "I'm forever grateful for the mau5's early support but the reality is sad. He's shriveling In his own pile of hatful
"I dont care bout ur personal career but the fact that u own ur own record label is sad. I feel sorry the artists you've signed.
"It's sad the people on your label have the worst label head ever aka you bro. (sic)"
However, Deadmau5 continued the argument by insisting it only takes "23 minutes" to make a radio hit with a "lil popstar".
He wrote: "tell you what. Lemme borrow the lil popstar for a week, mash together a radio hit in 23 minutes, and will be good label! Yay!
"In summary: 2 EDM sellouts b***hing about who's got a good label and or who's sad. Welcome to 2015. That's about all I'm getting outta this (sic)."
Continuing the argument, Skrillex added: "yes good night you sad old washed up a**hole.
"you can ignore bullying but at some point you have to stand up for yourself and your friends (sic)."