Arsenal boss Arsene Wenger was unhappy with referee Martin Hansson after seeing his side go down to a 2-10 Champions League defeat to Porto.
Wenger remonstrated with the official when Falcao scored from a quickly taken free-kick after keeper Lukasz Fabianski had been penalised for picking up a back pass from Sol Campbell.
Campbell had earlier cancelled out an own goal by Fabianski in the last-16 first leg.
“The backpass was accidental, it has to be intentional to be a free-kick,” said Wenger. “When the referee gives it he has to allow us a chance to defend it.”
With the scores level at 1-1 he turning point of the game occurred seven minutes after the break when Campbell, 35, played the ball back to his keeper.
Fabianski needlessly handled the ball and after the referee awarded an indirect free-kick, the hosts scored from a quickly improvised free-kick as the Arsenal defenders protested.
“What can you do about the second goal? Whenever do you see the defender kick the ball back with his toe? The ball hit Sol, it was not on purpose,” insisted Wenger.
“It is difficult to understand how the referee can interpret that. Then, on an indirect free-kick, if you allow the team to play quickly, just five metres from the goal, how can you defend that?
“It is better than a penalty. It was unbelievable that he allowed Porto to play straightaway and push the ball into the net. I have never seen that and I have been in the game a long time.
“From a situation where there was no goal chance at all, and no free-kick as well, the referee gives them just a goal.
Wenger refused to blame Fabianski, who was at fault for both Porto goals.
“I do not want to come out individually on Lukasz’s performance, and judge him in front of everybody,” added the Frenchman.
“You have to accept you lose as a team and win as a team. Any individual performance has not to be analysed publicly.
“It’s unfortunate that we lost the game but we are still in the tie. They played well but we have a chance to turn it around in the second game. That’s what we will try to do and I’m convinced we will do it.”
Porto coach Jesualdo Ferreira had little complaints about the manner of the winning goal.
“It was a legal goal, one born out of the intelligence of a Porto player,” said Ferreira.
“Thierry Henry also did the same thing when he played for Arsenal. It gives a definite advantage to Porto now in the tie.”