By ROBIN MIZRAHI

Britney Spears and husband Kevin Federline keep a high profile, but insiders say the couple's earning power is sinking fast.

Five years ago, Britney was ranked No. 1 on Forbes' Celebrity power list and earned $39.2 million — but last year the 24-year-old pop star's income was reportedly an estimated $4 million.

And it doesn't look like aspiring rapper Kevin will be raking in the dough with his new CD, due out in October. His recent performance at the Teen Choice Awards was universally panned. "All of Britney's hype for Kevin's single 'Lose Control' couldn't help his pitiful and embarrassing performance, "a showbiz source told The ENQUIRER.

"After 30 seconds on stage, people were actually giggling at him."

Brit's career is on hold as she takes care of son Sean Preston, who turns 1 on Sept. 14, and awaits the birth of her second child in just a few weeks.

And although Britney's far from broke — with a net worth of more than $100 million — insiders said she'll never again be the hot commodity who earned huge sums of money in the past.

Read all about it in this week's ENQUIRER!
Also in the issue: BRITNEY TO KEVIN: THE PARTY'S OVER!