A man was seriously injured after becoming involved in an argument at the Bijou Club in Manchester.
Police said a man was restrained after the row, but when he tried to break free, he was punched and hit.
The 31-year-old is in a serious but stable condition.
Guests at the club have included Justin Bieber, Tulisa, Drake and Rita Ora.
Greater Manchester Police asked for anyone with information to contact them.