The 26-year-old appeared on US chat programme The Tonight Show with Jay Leno on Wednesday saying that she thinks Middleton, 29, should throw or give away her clothes at the end of the day.??
The Duchess of Cambridge has been seen wearing some of the same outfits again and has been praised for recycling her wardrobe.
Osbourne said: 'Only in this country they call it a faux pas. In England, they're like, 'Look how thrifty she's being, showing the British public that the royals are in a recession as well.' I'm sorry, but if I had that job I would only wear it once.
'If I'm going to be the future bloody Queen of England, I'm gonna wear that dress once and that's it, because I'm giving the rest of my life, all of my privacy - at least I could wear a new dress every day.'
Kelly has since taken to her Twitter page to explain her remarks.
She wrote: 'I didn't talk s*** about Kate Middleton. Saying she deserves a new dress every day is not talking s*** last time I checked.
'I said 'deserves' not 'should have' or 'needs'. Why am I an a** hole because I think she deserves a new dress every day?
'I just don't get why they feel the need to even make stories up about me when I already do and say enough stupid s*** to last them a lifetime.'