Celtic confirmed on Tuesday that they had no plans to appeal against a UEFA fine imposed for "illicit chanting" during last month's Europa League clash with Rennes.
The Scottish giants were fined 15,000 euros by UEFA on Monday after police informed match officials that Celtic fans had engaged in chants supporting the Irish Republican Army during the game.
Celtic chief executive Peter Lawwell insisted that the supporters responsible represented a "tiny minority" of the club's fans.
"The heavy fine imposed by UEFA is an indication of the seriousness with which it treats such matters," Lawwell said.
"We would reiterate our own position that, however small a minority is involved, such chanting is not welcome at Celtic Football Club.
"Clearly, it is very disappointing and a source of real regret amongst our supporters that Celtic's proud history of exemplary conduct has been tarnished in this way by such a tiny minority.
"However, this is a clear warning that such behaviour will not be tolerated and together, Celtic Football Club and our supporters will do all we can to ensure that this incident is not repeated.
"We would like to thank our supporters for their magnificent conduct since the match against Rennes. We are proud of the fantastic and positive reputation we have established across Europe over many years, and the club and our fans will be doing all we can to ensure that this is protected."
Celtic earlier this month escaped punishment for similar chanting during an October 29 game against Hibernian after the Scottish Premier League ruled the club had taken all reasonable action to prevent the fans behaviour.