GIRLS rule at “The X Factor” – with BRITNEY SPEARS and DEMI LOVATO demanding “dinosaur” judge SIMON COWELL to get a makeover!

“It’s a real blow to Simon because he brought Demi and Britney onto the show to give it a younger feel, and now they’re telling him that he’s the dinosaur,” said a source.

Pop princess Britney, 30, and former Disney starlet Demi, 20, ganged up on the 53-year-old after British singing sensation Sophia Grace Brownlee, 8, ridiculed Simon for wearing his pants nearly up to his chest on Ellen DeGeneres’ show.

“Simon was already having a bit of a midlife crisis, so knowing people think he’s wearing mom jeans really blindsided him,” said the source.

“He’s always been proud of his dressed-down sense of style. He loves the jeans and T-shirt look or unbuttoning his collared shirts to show his chest.

“But fellow judge L.A. Reid is a sharp dresser and the girls always wear the latest trends. Simon doesn’t want to be thought of as a granddad!”

Adding to his fashion faux pas, the sharp-tongued former “American Idol” judge has faced some medical issues.

According to an updated version of the biography “Sweet Revenge: The Intimate Life of Simon Cowell,” he collapsed with “nervous exhaustion” earlier in the summer. His doctor reportedly ordered Simon to get some rest.

When he returned to “The X Factor,” Britney and Demi treated Simon “like an old man,” said the source.

“It was tough for him, especially since he’s always considered himself one of the world’s most eligible bachelors. It really bruised his king-size ego. Now the girls are pushing him to change it up, and he’s promised to try a few new looks.”