Wenger couldn't believe Olympiakos' equaliser was ruled legit.
He said: "We need a good Christmas present now. We'll simple as that. What is the referee doing behind the line? Nobody knows. They did not do their job in a serious way - all night we had some surprising decisions.
"They looked like they knew there was not too much at stake. If you do not question the role of the referee then you have to ask what is he doing.
"It is his job and it was so obvious that nobody had touched the ball.
"You wonder how he could not see that and what is worse, how could he see someone touch the ball when from 100 yards away you could see nobody touched it.
"It's too easy to say it cost us top spot, but it cost us a goal and changed the momentum of the game."