Cameron Diaz is shocked by Jennifer Lopez's huge entourage

When it comes to showbiz catfights, they don't get any more A-list than this.

Word from the set of Cameron Diaz and Jennifer Lopez's new movie What To Expect When You're Expecting is that the pair can't stand each other.

And it's got to the point where the normally chilled-out Cameron, 39, has been sniping to anyone who'll listen about 42-year-old Jen's diva attitude.

An insider on set in Atlanta, Georgia, tells Now: ‘Cam thinks J-Lo's a nightmare and gives movie stars a bad name.

'She's even said that Jen should stick to her day job, meaning American Idol and singing.

'Jen's constantly taking mini-breaks from the set to see her twins.

'She demands to eat at specific times, no matter what.

'So at 10.15am on the dot, she stops work and has an assistant run over to her with a small protein and veg-based meal.

'It's driving Cameron crazy.'

Read the full story about Cameron Diaz and Jennifer Lopez in Now magazine dated 5 Septmeber 2011 - out now! 

Now cover 5 Setember 2011

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