Arsenal manager Arsene Wenger accused referee Martin Hansson of a “massive mistake” in his side’s 2-1 defeat to Porto.
Wenger was furious that Hansson awarded Porto an indirect free-kick after Lukasz Fabianski picked up Sol Campbell’s back-pass.
And the official then appeared to get in Campbell’s way as Porto were allowed to take a quick free-kick to score their second goal.
“I believe it (the back-pass) was accidental, Sol touched it accidentally,” Wenger told ITV1. “And the referee should give us time to build the wall.
Asked if Porto should have been allowed to act so quickly, Wenger added: “Yes, in the middle of the field, but not in the box. We had no chance to defend.
“I think it was a massive mistake, it was a double mistake. It was a penalty for us as well when (Tomas) Rosicky went down just before.”
Hansson was also the referee who failed to spot Thierry Henry’s handball for France in their World Cup play-off with the Republic of Ireland, but Wenger would only add: “I just believe in a game of that magnitude I don’t understand his decision.”
Arsenal captain Cesc Fabregas conceded he might well have taken a quick free-kick under the same circumstances.
“Maybe as a player I would have done the same to try to score,” he said.
And the Spaniard admitted the Gunners also had themselves to blame.
“When you concede these goals you cannot go anywhere, schoolboy goals, what can you do?” he added.
“Maybe we are still a little soft in that aspect, as a team when we concede we are not strong enough to lift ourselves, we were not strong enough to stand up and play well.”