Harvey Weinstein is already being belligerent at sex addiction rehab — barking into his banned mobile phone and remaining in denial about his alleged sex attacks, insisting each and every one was consensual, Page Six has exclusively learned.

The movie mogul, who volunteered to go to rehab after a wave of allegations of sexual harassment and rape against him from women in Hollywood, isn’t exactly in his element in therapy, falling asleep in sessions or talking on his phone, a source tells Page Six.

Weinstein was reported to be at an inpatient facility, but our source says he is actually being treated at an intensive outpatient facility, which allows him to spend nights at a hotel. The clinic offers one-on-one counseling and group therapy sessions, among other treatments.

The source told us, “In one group therapy session, Harvey arrived 15 minutes late. Then, when it was his turn to speak, he launched into a speech about how this is all a conspiracy against him.”

The source added that as others at the clinic shared their personal stories, “Harvey fell asleep in his chair. He was only woken up by the ringing of his smuggled mobile phone [which is banned at the facility] . . . Harvey jolted awake, jumped up, immediately took the call and then ran out of the room.”

The events were said to have taken place Tuesday — the same day Weinstein resigned from the board of directors of his former movie company as his sex scandal widened.

Another source close to Weinstein says he is no longer joining group sessions, “for obvious reasons,” but is undergoing individual treatment, and is accompanied at all times by a therapist.

“He insists he never raped or assaulted anyone, and that all the encounters were consensual. He realizes he has acted like an a–hole, but he still insists he’s not a rapist. He does have his phone, but when he is in therapy, he has to give it to someone else,” the source said, adding, “The characterization of what he said and what happened at the group session isn’t true.”

His reps didn’t comment last night.