The duo, vocalist Alexis Krauss and guitarist Derek Edward Miller, took to Twitter.com on Monday (02Nov15) to suggest the star copied the tracks without their permission, admitting they were "flattered", but adding, "We were not contacted".
Lovato has not responded to the message, but producers Carl Falk and Rami, who have writing credits on the track, are dismissing the accusations.
"We did not use any samples in Demi Lovato's song Stars," a statement from Falk and Rami to Entertainment Weekly reads. "Demi was also not involved with the production. She only wrote top line."
Meanwhile, fans have come to Demi's defence with one writing, "@sleighbells @ddlovato The least you could do is attempt to be professional. Don't air your dirty laundry on the internet."
Another one added, "@sleighbells @ddlovato PLS (Please) CONTACT DEMI OR HER TEAM INSTEAD OF TWEETING HER ON SOCIAL MEDIA. UGHH".
However, some fans agreed with the band, writing, "it's pretty obvious that the drum samples were ripped straight from the song..."