Celtic chief executive Peter Lawwell demanded supporters leave their political views at home after Uefa began disciplinary action against the club over an "illicit banner".
Celtic face a fine over a fans’ display which featured banners of Scottish historical figure William Wallace and IRA hunger striker Bobby Sands along with a set of lyrics during their 3-0 Champions League defeat by AC Milan on Tuesday night.
The banners, which were displayed in and around the section housed by the Green Brigade group of supporters, read: “The terrorist or the dreamer, the savage or the brave, depends whose vote you’re trying to catch or whose face you’re trying to save.”
The club vowed to ban any supporter involved in a political display as Lawwell insisted they were not welcome at Celtic Park.
Lawwell said: “Last night was nothing more than clear disrespect for the club and our supporters who now face another Uefa charge.
“There have now been a number of Uefa charges made against the club during the last three years, relating to behaviour, displays and pyrotechnics – it cannot go on any further.
“Let’s be very clear. Following the actions of a small minority, these charges are made against the club.
“It is the reputation of Celtic, our great club and our great fans which is damaged, while others carry on indulging in such behaviour.
“Our supporters do not want this any more. We are a non-political organisation, a top football club in fantastic shape, aiming to play its part as a major football club on the European stage.
“Regardless of the political views people hold, football stadia, whether it is Celtic Park or anywhere else, should not be used to promote these. This is something which all football authorities, including Uefa, have stressed for some time and something well known by all supporters.
“The club don’t want it, our manager and our team don’t want it, our supporters don’t want it and the football authorities don’t want it – it has to stop.
“Celtic is a world-class football club and rightly proud of its wonderful reputation in the game. This is a reputation hard-earned by our supporters over many years. We cannot and will not allow this reputation to be tarnished any further.”
The club added in a statement: “During the last two matches at Celtic Park, banner displays have taken place which have not been approved by Celtic Football Club. These were displays which were in no way football-related and which have no place at Celtic Park.
“With regard to last night’s display, the club made it abundantly clear in advance to the group in question that only football-related displays would be permitted and that any political display would lead to a Uefa charge. We, in turn, received an assurance that all displays would be 100 per cent relevant to Celtic.”
A banner display at Saturday’s Scottish Premiership clash against Aberdeen featured a large ‘H’ and the lines “they fought and died for their wee bit hill and glen”.
Uefa earlier announced its control and disciplinary body would deal with the case on December 11th after confirming proceedings had been opened for “an incident of a non-sporting nature (illicit banner)”.
The European governing body referred to a rule that holds clubs liable for “inappropriate behaviour on the part of their supporters... even if they can prove the absence of any negligence”.
The “inappropriate behaviour” includes the “use of gestures, words, objects or any other means to transmit any message that is not fit for a sports event, particularly messages that are of a political, ideological, religious, offensive or provocative nature”.
Celtic were fined approximately €5,000 after supporters let off fireworks in their Celtic Park qualifier against Cliftonville in July.
They previously received fines for supporters letting off flares and displaying an offensive banner during a Europa League match at Udinese in 2011. The banner insulted Uefa days after the club were fined about for ”illicit chanting” involving pro-IRA songs at a game against Rennes.
