AN unlikely A-lister has trumped the likes of Lady Gaga and Justin Bieber to be crowned Forbes' Most Powerful Ladies Replica Watch Celebrity - in the same week she threw in her job.

Jennifer Lopez, who is rumoured to have quit her role as a judge American Idol, has topped the 100-strong list which ranks stars based on a combination of earnings, press coverage and internet presence.

Up from 50th place last year, her role on the singing contest is said to have would have contributed greatly to her "power" but it seems the star feels has too much on her plate.

"She's just too busy," a source told E! News.

Lopez is also set to tour with Enrique Iglesias this summer when Idol auditions kick off as well as balance her singing career, Hollywood roles and being a mum to four-year-old twins Emme and Max.

The 42-year-old beat the likes of television presenter Oprah Winfrey (second) Justin Bieber (third) and singer Rihanna (fourth).

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Lady Gaga came in at number five, toppled from her number one position last year.

Forbes said many on the list showed business acumen as well as stage talent.

For example, 18-year-old Bieber "is also a serious investor, with stakes in a dozen companies that appeal to his tech savvy, including a chunk of Spotify".

"Numerous celebrities are leveraging their fame to make early-stage investments or launch start-ups themselves," the magazine said.

But the best example was J-Lo.

Her success as a judge on American Idol, a resurgence in marketing her music, and an attention-grabbing divorce from Marc Anthony, followed by lucrative product endorsement deals, have sent her financial star shooting.

"While she hasn't stormed Silicon Valley just yet, Jennifer Lopez is a state-of-the-art celebrity success story," Forbes said.

"With $US52 million ($52.47 million) in earnings over the last 12 months and a massive amount of fame, Lopez lands at number one on our Celebrity 100 list for the first time."

Overall, the earnings power of the top 100 dropped in 2012 to $US4.4 billion from $US4.5 billion.

Winfrey was still the most lucrative star, earning $US165 million, although that was well below her $US290 million haul last year.