"Enough is enough. He was clearly in breach of club rules," said Blackwell of 26-year-old Oster. "Enough is enough, whilst I am in charge I will not have players besmirching the club's reputation.
"The player has stepped out of line and I want us to be seen to do something about it. This club is bigger than any player.
"When people write about my players on the back pages I want it to be for what they're doing right on the pitch and not for anything else.
"Leeds United will not put up with shenanigans from any players."
Jamie McMaster was also fined and Leeds have issued a warning as to his future conduct.