Kelly Osbourne: I was NEVER as fat as Christina Aguilera

The Fashion Police star once again took aim at her arch-enemy’s weight after reviewing footage of Aguilera wearing a trouserless all-in–one with knee-high boots at last weekend's Michael Jackson tribute concert.

Osbourne, 26, said: 'She called me fat for years. I was never that fat.'

The show’s leading lady, Joan Rivers, didn’t hold back either, quipping that, 'Lady Marmalade got into the peanut butter again'.

Co-host George Kotsiopoulos tried to be a tad more diplomatic. 'I'm looking at this and thinking, 'Well, she's put on weight. This just isn't flattering,” he said. “But this is just a crappy outfit, regardless. No matter what shape your body is in, it's just bad. [She is] still probably a size 2/4.”

But Osbourne was having none of it. 'Trust me,' she said. 'I'm a 2/4. That is not a 2/4.'

Just last month Osbourne – who lost 48 lbs after competing on Dancing with the Stars - laid into Aguilera on the show, calling her a 'fat bitch'. 'She called me fat for so many f***ing years,' Osbourne said. 'So you know what? F**k you! You're fat too.'