Paris Hilton is declaring war on her former best friends, the Kardashian sisters, for becoming more famous and earning more cash than she does.

The hotel heiress is fuming that Kim and her sibs, who got their first big break by hanging out on the Hollywood scene with Hilton, have eclipsed her in the fame and money stakes. Sources say she’s hatched a plan to boost her brand by pushing a new beauty line and make herself more likable by playing down her lavish lifestyle.

A source told Page Six: “Paris is furious that Kim got her start by hanging out in Hollywood with her — and now, the Kardashians have it all, the reality shows, the magazine covers, the big appearance fees and promotional deals.”

“She used to command $100,000 for club appearances, but now Kim is the hottest girl — and they aren’t friends anymore. The magazines are bidding around $300,000 for Kourtney’s baby-shower and baby pictures. And Khloe’s wedding brought in record ratings for E!”

“Paris has realized that standing for excess in a recession doesn’t appeal,” our insider continued. “The Kardashian girls seem more real, and girls identify with them more. She’s got to ditch the pink Bentley and concentrate on developing herself.”

Sources close to Hilton said she’s carefully working on the launch of her new hair and beauty line, which she’ll unveil in Beverly Hills on Tuesday, taking the lead from the Kardashians by having her family at her side. And she’s keen to play up her more stable relationship with Doug Reinhardt and talk about the possibility of marriage and babies.

The source added: “Paris has 15 product lines on sale. She isn’t really a party girl anymore, she is quite settled with Doug. She wants more people to appreciate that she’s grown up.” A rep for Hilton declined to comment.