The loss was United's first in the Premier League since their defeat to Everton in the opening round of matches.
"They gave us four minutes [of injury time], that's an insult to the game," he is quoted as saying by the BBC. "It denies you a proper chance to win a football match.
"There were six substitutions, the trainer came on, so that's four minutes right away and the goalkeeper must have wasted about two or three minutes and they took their time at every goal kick.
"That's obvious to everyone today and it's a flaw in the game that the referee is responsible for time keeping. It's ridiculous that it's 2012 and the referee still has control of that."
United are now third in the league table with 12 points from six matches, four points behind leaders Chelsea.