Kelly Osbourne certainly wasn’t shy in revealing how she feels about her nemesis Christina Aguilera.

While shooting a segment for E!’s Fashion Police segment, the reality star criticised her rival’s fuller figure by calling her a ‘fat b****.’

Commenting on a photo of the singer wearing a tight black dress, the 26-year-old sniped; ‘Maybe she’s just becoming the fat b***h she was always born to be. I don’t know. She was a c*** to me.’

Fired up: Kelly Osbourne called Christina Aguilera fat on E!’s Fashion Police

OMG: Kelly shocks E!’s Giuliana Rancic with her comments about rival Christina

The cattiness didn’t stop there. ‘She called me fat for so many f**king years, so you know what? F**k you, you’re fat too!’ she added.

She wasn’t the only one on the panel to criticise the 30-year-old singer, whose weight has yo-yoed since the birth of her son Max in 2008.

Joan Rivers laid into the blonde bombshell, saying: ‘She looks like Snooki’s Scandinavian cousin. It’s a pretty dress but she’s stuffed into it.’ 

Curvy girl: Ozzy’s daughter mocked The Voice judge for having a slightly fuller figure as she promoted her new fragrance Royal Desire in Munich last month

Rivals: Kelly and Christina sparred at the MTV Europe Music Awards in Edinburgh, Scotland, in 2003

Kelly and Christina have famously feuded for years.

Back at the MTV Europe Music Awards in November 2003, the network even aired a skit of Christina throwing darts at a photo of the British personality.

When she took the stage, she mocked Ozzy’s daughter as well, saying: ‘Oh Lord, I didn’t realise it was still Halloween.’ 

But The Voice judge isn’t the only person Kelly is sparring with over weight these days. However, given that her body is the source of ridicule might make her a bit more forgiving towards someone else.

While she was attending Amy Winehouse’s funeral last week, her ex-fiance Luke Worrall posted a series of cruel tweets making fun of her figure.

He deleted them mere hours later, but a furious Kelly couldn’t resist retaliating over Twitter. 

Pop shots: Joan Rivers mocked the blond bombshell on E!’s Fashion Police as well

Demure: Kelly looking elegant as she records the Tonight Show with Jay Leno in LA today

‘@luke_worrall you’ve made it very clear u only dated me 4 my life style but s**t tweets about me the day im @ a funeral u have hit a new low.

‘It was fine when my Kellyphant ass was paying 4everything wasn’t it? i just didn’t think u could get much lower but u did #wow.’

She posted the following quote on her page on 30 July: ‘Any fool can criticize, condemn, and complain but it takes character and self control to be understanding and forgiving.-Dale Carnegie’