A war of words erupted between O'Connor and Cyrus this week (begs30Sep13) when the Nothing Compares 2 U hitmaker penned an open letter to the controversial 20 year old, advising her to stop stripping off and acting provocatively on stage and in her videos.
Cyrus nonchalantly hit back by comparing her to troubled actress Amanda Bynes before uploading a string of Tweets O'Connor wrote in 2012 when she was dealing with a bout of depression.
O'Connor angrily attacked the star in a further two letters, accusing her of mocking the mentally ill and threatening her with legal action - and now she has unleashed her fury at another pop hot shot.
Appearing on Ireland's The Late Late Show on Friday (04Oct13), the star singled out Cowell and his pal Louis Walsh, insisting they have wreaked havoc on the music industry with their talent shows and manufactured acts.
She told host Ryan Turbridy, "I think the important thing to say is there's a certain alarm that needs to get rung and I know there are a lot of musicians around the country and around the world that will agree, music is being murdered, rock and roll is being murdered.
"The power of rock and roll to change things, to move people, is being murdered by all of this worship of fame, Pop Idol, X Factor, all this stuff.
"People like Simon Cowell and Louis Walsh - who doesn't even know how to burn a Cd as of the last time I saw him - deciding what records should sound like, and deciding who gets to be famous and who doesn't."