Updated

The Barbie-and-Ken couple who invited America to watch them struggle through their first year of marriage on national television are apparently a couple no more, according to a celebrity magazine.

After months of rumors that their relationship was on the rocks, Jessica Simpson (search) and Nick Lachey (search) are breaking up, Us Weekly reports in its current issue, with the headline "Split!"

News of the forthcoming story prompted reps for Simpson, 25, and Lachey, 31, to do what they've come to do best these days: deny it.

"Nick and Jessica have not separated," said a joint statement on behalf of the couple released Wednesday. "Rumors to the contrary are simply not true."

"They have not separated," Simpson rep Brad Cafarelli said in an e-mail to The Associated Press.

Alex Dudley, a spokesman for Us Weekly, said the magazine was standing by its story.

The pair catapulted from nominally well-known singers to superstars with the MTV reality show "Newlyweds: Nick & Jessica" (search), which followed them through the trials and tribulations of their new life together as husband and wife.

The program made Simpson, who’d previously had a Top 40 hit with "Irresistible" (search), everybody’s favorite ditzy blonde du jour — especially after she mistook “Chicken of the Sea” tuna for actual chicken in one episode.

Lachey, a former member of boy band 98 Degrees (search), came to be known as the more down-to-earth, mature half of the couple.

Us Weekly blames most of the pair’s marital problems on Simpson, saying her prima donna behavior, wild lifestyle and manager-dad were major factors in the split. The story says the separation happened over the weekend.

The magazine cover promises "details on Jessica & Nick's last days — and how her ego, partying and dad drove them apart."

The couple, who married in October 2002, don’t plan to announce their separation until later this month, according to Us Weekly.

The celebrity tabloids have been predicting the Nick-and-Jessica downfall for much of the past year, obsessing and speculating endlessly about their happiness — or lack thereof. Various magazines have run photos recently of both Simpson and Lachey without their wedding rings.

E! Online even printed and then quickly retracted a story about their impending divorce in May.

The couple have repeatedly insisted that they love each other and things are going swimmingly in their marriage. Lachey described the home front situation as "absolutely wonderful" in August, dismissing buzz about a breakup.

Simpson recently starred as Daisy Duke in "The Dukes of Hazzard" (search), which hit theaters this summer. Lachey had a recurring role on the TV show "Charmed" (search) and a small part in the movie "Bewitched" (search), which came out earlier this year. He just finished filming “The Hard Easy.”

The Associated Press contributed to this report.