Sharon Osbourne has blasted a comedian who called her daughter Kelly 'unattractive and fat'.

The feisty matriarch - who has a penchant for firing off poison-pen letters to those who dare cross her - sent a scathing email to Jim Jeffries, telling him to 'f*** off'.

Potty-mouthed Aussie comic Jim clashed swords with Kelly during this year's inaugural NME Awards USA.

But he has now revealed the fallout from daring to criticise the Osbourne clan  -  even in jest  - and the frank and hilarious exchange of emails between him and Sharon.

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Raging: Sharon Osbourne went on the attack with an Aussie comic who said her daughter Kelly, seen left, was not as attractive as model Agyness Deyn

Nobody: Comic Jim Jeffries received an email from Sharon telling him to f*** off

He was presenting awards in April and had made a joke to Kelly that she wasn't as attractive as Agyness Deyn, who had just left the stage.

The 23-year-old responded with a string of expletives, to which Jim replied drily: 'I think she'd be famous even if she wasn't Ozzy's daughter - she's that good.'

Kelly then spat in his face (charming). If that wasn't enough retribution, Jim said: 'I thought that would be the end of it but I got an email from Sharon which said, 'Dear Nobody. Wait until you're a celebrity before you criticise REAL celebrities. Why don't you f*** off '.'

But Jim hit back by replying: 'Dear Sharon. After you had all that plastic surgery and had the fat sucked out of your thighs, why did you pump it into your daughter's face?'

The comedian revealed the email rant at a gig in Shepherd's Bush last night, where he was warming up for his appearance at the Edinburgh Festival next month.

Sharon's spokesperson refused to comment.