Arsenal boss Arsene Wenger has criticised Michael Oliver's refereeing in Sunday's 3-1 Premier League defeat at Manchester City.
The Gunners boss disagreed with the awarding of a penalty for Nacho Monreal's challenge on Raheem Sterling, while David Silva was marginally offside in the build-up to the third goal from Gabriel Jesus.
City's win has moved them 12 points clear of Arsenal at the top of the Premier League after scoring 38 goals in their first 11 league games, and Wenger admitted that Pep Guardiola has put together a "top team".
"Can anyone stop them? It will be difficult this season, the way they have started the quality they have, but you never know," Wenger told reporters. "If on top of that they have decisions at home like that, they will be unstoppable.
"Overall, once again, the referee made the decision with a penalty and an offside goal. We are used to it when we come here. I feel they don't work enough, because it happens every season. It is unacceptable.
"You have seen what I have seen. The fact you tell me it is an offside goal says enough. I don't want to take anything away from the quality, but it happened at a moment when we were really in the game at 2-1 and it killed the game.
"It is the second year. We got two offside goals here last year and one this year. We put a lot of effort in and at 2-1 I thought we could come back. The 3-1 was an immense relief for them, an unexpected present. Of course, they are a top team, but that makes it even more difficult for you."
Up next for Arsenal is the North London derby against Tottenham Hotspur on November 18 after the international break.