from www.tmz.com – Montana Fishburne faked a suicide attempt and it was all caught on video … TMZ has learned.

Sources tell us that last August, Montana’s dad, Laurence Fishburne, was so concerned about his daughter’s well-being that he had a private investigator follow her around. The investigator shot video of Montana drinking what appeared to be bleach.

Turns out, Montana faked the whole thing. Sources say she found out a P.I. was videotaping her and drank the bleach “to put on a show.”

The tape has become relevant in the ongoing criminal assault case against Montana because her lawyer, Shawn Chapman Holley, had sent the tape to the prosecutor to demonstrate her client’s troubled mental state and help get a plea deal that involved rehab, not jail time. The prosecutor agreed to the deal, but has since disavowed it and wants her to do jail time.

The prosecutor argues in legal papers, obtained by TMZ, that the video “was just a ploy by the defendant to manipulate the People to offer a more lenient sentence.”

But we’ve learned, shortly after sending the video to the prosecutor, Holley learned it was fake and actually notified the prosecutor everyone had been duped by it.

Holley is asking the judge to enforce the original deal — rehab and no jail. The prosecutor is steadfast and does not want to honor that deal.