Roberto Mancini was unhappy with the award of a penalty to Fulham during Manchester City's 2-1 victory at Craven Cottage.
City came from behind in West London to claim the points after substitute Edin Dzeko scored a late winner after Sergio Aguero had cancelled out Mladen Petric's early spot-kick.
The penalty was given following Pablo Zabaleta's challenge on John Arne Riise, but Mancini felt the foul took place outside the box.
"It was difficult because it wasn't a penalty," Mancini told Sky Sports. "After about 20 minutes you are 1-0 down with a penalty that was not a penalty.
"You saw everything. My opinion was that it was out [of the box] and it was no foul, no penalty."
City boss Mancini claims the incident was the latest in a number of recent decisions that have cost the Premier League champions.
He added: "We can do nothing. There were a lot of mistakes in the past four games. We accept this, but we're not happy. This is true but we can do nothing, only continue to play.
"Sometimes it is a penalty but the referee is there to take a decision. Sometimes he does well, sometimes he can do bad.
"If we go to watch all our last three games, against Stoke it was handball. I don't know why the referee that was behind didn't give it. Against Arsenal there was one penalty."