The officials who allowed two offside goals to stand in Celtic's 3-0 Champions League defeat at Manchester United have conceded they were wrong.
Belgian referee Franck De Bleeckere and his assistants failed to chalk off two Dimitar Berbatov goals.
Assistant Alex Verstraeten said: "I admit to the mistakes, but we also ask for understanding. Offside decisions are the hardest to judge.
"It is our bad luck that the mistakes came at goals."
Berbatov opened the scoring in Tuesday's Group E clash at Old Trafford from an offside position.
The Bulgarian striker doubled the home side's advantage when a Cristiano Ronaldo shot rebounded to him in the Celtic box; Berbatov knocked the ball home from close range having stolen a yard on the Celtic defence.
The match officials also wrongly ruled out a Wayne Rooney strike for offside.
"This is the first time that we have made a mistake in 52 international matches," Verstraeten said.
"It is no consolation that Manchester United would have won without these decisions.
MY SPORT: DEBATE"Some players argue their case in front of us, but no Celtic player protested.
"That proves that the offside decisions were very tight. At the end of the match, I was surprised when I saw the television images."
Referee De Bleeckere added: "At the moment itself, we were not aware of the error.
"There was no protest. I walked off the field with a good feeling. But, when you see the images, it's a shame.
"The officials are a team. We did okay at the European Championships and in the Champions League. We must help each other and see it as a learning curve."
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