The Achy Breaky Heart hitmaker - who is currently divorcing wife Tish - took to twitter following the video of 18-year-old Miley smoking salvia from a bong.
He wrote: 'Sorry guys. I had no idea. Just saw this stuff for the first time myself. I'm so sad. There is so much beyond my control right now.'
Anthony Adams - a former California State Assemblyman who previously tried to ban the drug in his state - believes salvia, which is legal in a number of US stars, can make people do 'crazy' things and has blasted her for being irresponsible to her legions of young fans.
He said: 'You do incredibly crazy things. Miley is a star and young kids are going to emulate her behaviour.'
In the video taken of Miley smoking the drug, she is seen confusing a party guest for Last Song co-star and ex-boyfriend Liam Hemsworth as well as giggling uncontrollably.
She said: 'OK, I'm about to lose it now. I'm having a little bit of a trip right now.
'Oh my God! He looks so much like him! He looks so much like Liam. Is that me tripping? He doesn't look like Liam at all? Dude, that looks
just like Liam!'