“American Idol” producers and nasty judge Simon Cowell keep the young contestants under virtual house arrest and work them from sunrise until nearly 2 a.m. every day!

That’s the dark secret behind America’s No. 1 TV show, an ENQUIRER investigation reveals.

“These poor kids are nothing but slaves — puppets on a string,” an insider declared.

“The producers plucked them from small towns across America and waved stardom in their faces. The result was they signed them to contracts that are little more than legal slavery.

“Some of the contestants were actually relieved when they were voted off because they were nearing nervous breakdowns over the stressful conditions.

“For the past three months producers have led these kids around by the nose, forcing them to submit to grueling rehearsals that drag on eight hours a day or more.

“It’s a vicious treadmill of rehearsals, voice coaching, styling and nonstop promotional appearances. They are up before 6 a.m. so they can do radio shows for the East Coast and it doesn’t stop until 2 a.m. the next day.

“Producers made deals with corporations for the kids to hawk their products and have sent them on endless photo shoots for merchandise like posters and coffee mugs — even if it means working them to the bone.”

Before she was booted off the show, Christina Christian ended up in the hospital due to stress-related dehydration and a sinus infection.

And finalists Kelly Clarkson and Justin Guarini have lost at least 10 pounds in the past month, the insider revealed.

“Poor Kelly had to drink a big shot of olive oil before each performance because her throat was so raw.

“And in the show’s final two weeks, Justin and Kelly were shuttled between their hometowns and the coasts so often, their only sleep was on the plane ride!”

When the performers aren’t working they are virtual prisoners in the house that was rented for them, the insider disclosed.

“They aren’t allowed to leave the house without permission and chaperones, and producers even took away Ryan Starr’s car so she couldn’t go anywhere. It’s like being under house arrest!”

The house looks attractive on the outside but inside there are busted windows, poor plumbing and a broken elevator, revealed a source close to the show.

“It’s a five-story house and the elevator doesn’t work, so after a 20-hour day, the kids are practically crawling up the stairs to their bedrooms.

“All these kids ever wanted to do was sing their hearts out. But their dreams of stardom have resulted in broken hearts and broken spirits.”