Peter Lawwell revealed Celtic fans have cost the club more than 500,000 euros in UEFA fines as he explained the self-imposed closure closed of a part of Parkhead for Thursday's Europa League clash with Rennes.
The Scottish champions were fined £12,900 by UEFA on Friday after fans displayed an "illicit banner" and sang obscene chants during their Europa League game at home to Lazio last month.
It was Celtic's third charge of the season and with another hanging over the club for fans using pyrotechnics during the win over Lazio in Rome on November 7.
That will be the 20th charge since 2007 and the Parkhead board acted by closing rows A to M in the rail seating section of the stadium which holds the club's ultras, the Green Brigade.
Speaking at the club's AGM at Celtic Park, the club's chief executive Lawwell said: "Over the years in terms of UEFA, we have actually been fined over 500,000 euros and that can't go on.
"So we have had to take that action on the basis of what might happen if we don't.
"You saw today that Feyenoord fans have been banned from travelling abroad which would affect all our supporters in terms of European travel.
"So we had to take action to prevent further possible stricter action from UEFA.
"We have the responsibility first for safety and secondly to protect the reputation of the club and the supporters have that as well.
"We are all proud of our reputation around the world and I am sure the supporters are.
"For the vast majority of times over there (Green Brigade) it is colour, atmosphere, energy and youth and it's fantastic but there are times when a small minority let us down.
"The unfortunately concerning thing for us, is that they don't seem to believe they are doing anything wrong.
"So in terms of overcrowding, pyrotechnics, abusive banners, abusive singing and alcohol in the stadium, these are things that just cannot go on.
They are against the law, they are against ground regulations and they are against the rules of the competition."
Lawwell stressed that safety and reputation were the club's two main concerns.
He said: "The reputational things for me is important. "You see a banner or hear a song and your heart just sinks.
"That's not who we are and it does give our enemies the opportunity to class us the same as other clubs and portray us as two side of the one coin which we are not. We are different.
"But again, unfortunately, a small minority are a challenge.
"A challenge in terms of safety inside the stadium and also protecting that reputation of our magnificent club.
"It is a difficult challenge. There are societal changes, there are people who come to Celtic Park and in some way show their frustrations in terms of their life, and there are societal issues in terms of alcohol abuse and drug abuse that manifest themselves at the football, social misbehaviour.
"For us, safety is everything here.
"We built the standing section, the rail seating for safety and we have to keep our people safe and we have to also protect our reputation."
