Lady Gaga has apologised for working with embattled R&B star R Kelly, and vowed to remove their duet, Do What U Want, from streaming services.It comes after the broadcast of a new documentary about Kelly, which detailed allegations of sexual and physical abuse against women and underage girls, spanning several decades.Gaga called the stories "horrifying" and "indefensible", adding: "I stand behind these women 1000%".Kelly has denied all the allegations.His lawyer also dismissed the documentary as "another round of stories" being used to "fill reality TV time".But film-maker Dream Hampton said the film depicted how Kelly had "built an ecosystem around his predation", after almost three decades of "preying on young and vulnerable women".