Samuel L Jackson has warned that Barack Obama should "be a leader" and stop "trying to relate".
The Pulp Fiction star took issue with the United States President dropping the Gs at the end of his words.
Jackson said: "We know it ain't because of his blackness, so I say stop trying to 'relate'. Be a leader. Be ****ing presidential."
Jackson continued his tirade, saying: "Look, I grew up in a society where I could say 'I ain't' or 'what it be' to my friends. But when I'm out presenting myself to the world as me, who graduated from college, who had family who cared about me, who has a well-read background, I ****ing conjugate."
Jackson, who campaigned for Obama in the 2008 presidential election, said he still thought the President was a "safe dude" but was aware he faced a difficult fight against the Republicans.