The 18-year-old Disney star - already seeking help for personal issues and seen in racy leaked photos - is angered at reports that she filmed sex sessions.
"Perpetrating these completely unfounded rumors from supposed sources while Demi is in treatment dealing with serious physical and emotional issues is disgusting," her spokesman said.
"The sourcing on this report is so spotty that it is hard to fully respond."
The spokesman also rubbished reports that Demi's uncle, Francisco Lovato, acted as a chaperone who would keep people away from her tour bus while she had sex.
"Francisco Lovato is the brother of Demi's estranged father. He never travelled on the tour, and certainly didn't serve as some sort of chaperone," the spokesman insisted.