Los Angeles - Kelly Osbourne has lashed out at Katie Hopkins on Twitter.
The Fashion Police host has slammed the former Apprentice contestant after the controversial star accused her of cashing in on the success of her parents Ozzy and Sharon Osbourne, prompting Kelly to hit back with a foul-mouthed rant, calling her "insignificant" and ignorant.
Kelly - who appears to have only just realised Katie had poked fun of her mother's plastic surgery last December - raged: "U R a hypocritical vile human that is addicted 2 attention U R so insignificant! Don't you ever talk about my mother again!#India."
Katie retorted: "Just like Peaches and Jesus, Kelly has done well due to a famous parent. @KellyOsbourne".
This didn't sit well with Kelly - who was recently named by Forbes magazine as one of 30 most influential people under 30 in Hollywood - as she hit back: "Think John Lennon said it best "One thing you can't hide is when you're crippled inside." I feel sorry for you & Ur ignorance!
"Just like you can't help the parents you came from neither can I! I don't see you on a @Forbes list I work my bum off nice try...
"I know that what I am about to say is unbecoming of a lady & Im sorry to say this but I can't lie you are a massive #cunt. (sic)''
The war of words continued when Katie snidely retorted by mocking Kelly for being unladylike.
She posted: "No problem Kel. No one ever mistook you for a lady sweetie pie."
Kelly fumed: "You can shove your sweetie pie up your ass you insignificant t**t! Karma will get you! bloody hell you are so such a sad ass!
"actually made my night that @KTHopkins considers herself a lady when I think of her a desperate sad old bitter child is what comes to mind. (sic)"
The newly-single star - who split from her fiancé Matthew Mosshart earlier this month - appears to have taken offence to when the This Morning
regular mocked X Factor
judge Sharon's extensive plastic surgery in her Best magazine column last month.
Katie wrote at the time: "If she is going to look this good next year she will need to bulk buy plastic."