Celtic have warned the Green Brigade that Parkhead could be closed if they continue to stand during games.
The club urged all supporters to remain seated during matches claiming that the stadium's safety certificate was at risk. However, the warning is effectively aimed at the 'ultras' section of the Hoops support known as the Green Brigade who congregate in the Lisbon Lions stand and who provide most of the noise and colour at home games.
A spokesperson for the club told the club's official website: ''Clearly, the comfort and safety of spectators is our primary concern and it is essential that the issue of standing is addressed
''Celtic Park is designed specifically as an all-seater stadium and the Safety Certificate for operating has been approved and issued on this basis. Persistent standing is a real safety risk and could ultimately result in the Safety Certificate, which is required to open the stadium, being revoked.
''It is vital that this matter is taken very seriously and that supporters, for their own safety and the safety of others, sit down during matches.''
A spokesperson for Strathclyde Police said: ''The issue of standing during matches is one which must be taken very seriously. There have been a number of examples of this in recent weeks at Celtic Park and this cannot be allowed to continue.
''For their own safety and the safety of others, all supporters should sit down during matches. The Stadium Safety Team are rightly taking a very close interest in this matter.
''Celtic FC, Strathclyde Police and the Safety Team do not wish in any way to prevent supporters from enjoying football matches, however, the safety of those attending must be paramount at all times.''
Celtic officially sanctioned the Green Brigade's presence at Parkhead by allocating them a section of the stadium. However, there has been tension between the club and its hardcore fans since an anti-poppy banner was displayed by the Green Brigade during half-time of the 9-0 win over Aberdeen in November.
Celtic later said in a statement: ''The actions of this small minority have no place at Celtic Park. We are currently investigating the matter and, clearly, we apologise for any offence caused.''