In the video, obtained by TMZ.com, the singer/actress is seen inhaling huge lungfuls of smoke, reportedly from the burning of controversial but legal psychoactive plant Salvia.
The clip has caused a stir online and her entertainer dad Billy Ray has now waded into the controversy, apologising to fans for Miley Cyrus' behaviour.
Taking to his Twitter blog on Friday (10Dec10), he writes, "Sorry guys. I had no idea. Just saw this stuff for the first time myself. Im so sad. There is much beyond my control right now."
Billy Ray Cyrus split from Miley's mother, Tish, in October (10).