Arsene Wenger believes UEFA need to overhaul the way they choose referees after accusing Sweden's Martin Hansson of not being competent.
The Arsenal manager insists Hansson was wrong to allow Porto's second goal against the Gunners in the 2-1 Champions League defeat in Portugal on Wednesday after giving an indirect free-kick in the box following a back pass by Sol Campbell which goalkeeper Lucasz Fabianski picked up.
Wenger said: "It has to be clarified first of all how they nominate referees for games. They (UEFA) have to be much more open on how they rate their referees. Nobody knows really how they name their referees.
"Where is the ranking of the referees? I believe too much has gone on in the last 30 years. What has happened is not good for football."
When asked if Hansson, the referee who missed Thierry Henry's notorious hand ball in France's World Cup qualifier against the Republic of Ireland, should be refereeing at Champions League level Wenger said: "I don't know. Usually I trust the referee. But he missed a 100% penalty on Rosicky. That is a judgement in a second that I can accept. For me, the back pass of Sol Campbell was accidental.
"He has judged it is voluntary. Ok we have a difference there. That I can accept. Technically so many mistakes. His body position. Where he stands is completely wrong at the moment he gives a free-kick.
"He takes the ball from Lucasz Fabianski. They score. What he does doesn't make common-sense and is against the rules of the referees. So when a guy makes so many technical mistakes that is not even linked to judgement, I believe he is not competent.
"I trust the referees to do their job and to do it well. I never ask who the referee is before a game but in this case I cannot say that he made everything right because he was wrong.
"It's not my job to judge is he good enough or not, I just feel in that game he has shown he is not competent."
Wenger backed under-fire goalkeeper Fabianski but refused to say whether he would play against Sunderland tomorrow. First choice goalkeeper Manuel Almunia was due to have a fitness test on his injured finger today.
Meanwhile, William Gallas will be out for another fortnight with a calf injury and Campbell is set to to deputise again on Saturday.
Alex Song is due to come in after Abou Diaby was ruled out with a knee injury.
On Fabianski, Wenger said: "We have to show support to him and solidarity. It is a good opportunity for us to show that we are a special club and that we have a special togetherness and that we win and lose as a team.
"We live with opinions of people and everybody is entitled to theirs. But I believe in the keepers I have."