Whitney Houston, Bobbi Kristina

WHITNEY HOUSTON came up with the perfect plan to keep her daughter Bobbi Kristina off of drugs – but the pop diva’s gambit has backfired.

Since arriving in Los Angeles to film a new reality show – which focuses on the 18-year-old’s efforts to break into the music business – Krissi has stunned Whitney by spending time with Montana Fishburne, the porn star daughter of actor Laurence Fishburne.

Montana's only 19, but she already has a checkered past. Besides starring in a porn movie, she has been arrested for prostitution and ordered into rehab after beating up her boyfriend’s ex-girlfriend.

“Whitney thought she was getting Krissi away from her loser druggie friends in Atlanta by keeping her busy shooting a reality show in L.A.,” divulged a close family friend. “But now she’s hanging out with more troubled people!

“Krissi’s even telling Whitney it would be fun to appear in a porn video with Montana!

"hitney doesn’t know which way to turn.”

For the full story it’s in the new ENQUIRER!