Ferguson received the punishment when he appeared before a Football Association disciplinary panel at Wembley Stadium on a misconduct charge.
After his team drew 2-2 with Sunderland on October 3, Ferguson said referee Alan Wiley was not fit enough to handle the game. Although he later apologized, the FA banned Ferguson from the bench for two domestic games and left two more suspended until the end of the 2010-11 season.
Ferguson will need to monitor his conduct or the remaining two-game ban will be enforced.
"The Commission considered his admitted remarks, in the context in which they were made, were not just improper but were grossly improper and wholly inappropriate," said Peter Griffiths, chairman of the disciplinary panel.
Ferguson said in a TV interview after the game he was concerned about Wiley's fitness.
"He just wasn't fit enough for a game of that standard," the United manager said. "The fitness of the players, the pace of the game demanded a referee who was fit. He took 30 seconds to book a player, I think he's taking a rest writing down names on his card."
Ferguson apologised for "any personal embarrassment" by criticising Wiley, but maintained that the fitness levels of referees did not match the demands of the modern game.
