JESSICA SIMPSON has scored a stunning vic­tory in her battle of the bulge against KIM KARDASHIAN – by nailing an $8 million Weight Watchers con­tract!

Both are new moms, and reality diva Kim was courted by the weight-loss compa­ny. But sources say Weight Watchers execs balked after the money-hungry Kardashian turned down their $5 million offer. Meanwhile, Jes­sica’s $4 million deal as the company’s spokeswoman had been put on hold when she got pregnant with her second child last year – but now they’ve decided to double that!

“Jessica nailed it,” an insider told The ENQUIRER. “She played the waiting game and made out like she didn’t re­ally care. When Kim turned up her nose at the $5 million offer, Weight Watch­ers realized they needed Jessica back. They were so desperate they basically doubled her money.”

Now, sources say Jessica, 33, is deter­mined to show up Kim, 32 – who gave birth to boyfriend Kanye West’s daughter North on June 15 – in the weight-loss department too.

“Jessica might have talked about feeling sorry for Kim because of all the criticism she received about her weight during her preg­nancy, but in reality Kim spurred her into action,” revealed the insider. “Now that Weight Watch­ers has chosen her, she’s determined to slim down faster than Kim.”

Jessica’s baby daddy is her fiance Eric Johnson, a 34-year-old former pro football player who also fathered her 1-year-old daughter Maxwell.

The insider says that Jessica – who gave birth to son Ace on June 30 – has signed a one-year deal with Weight Watchers and her ads will be de­buting in late October.

“The big deal has really motivated Jessica to lose weight,” said a family friend. “She’s got a wed­ding to think about too. She really wants to be down to her Daisy Duke’s size 2 for that!”