French football chief Frederic Thiriez has promised swift and strong action against the 'imbeciles' among the Paris St Germain supporters who unfurled a controversial banner during the Coupe de la Ligue final.
PSG's last-gasp 2-1 win over Lens at the Stade de France on Saturday has been overshadowed by the banner, which was on display for around five minutes during the second half of the match.
It read: 'Paedophiles, unemployed, inbreeding, welcome to the North.'
The message hijacked the name of a film which is currently out in France, called 'Welcome to the North.'
The banner was aimed at the people of Lens, a small industrial city in the Pas-de-Calais region.
Both Lens and PSG have condemned the banner, while the Ligue de Professional Football (LFP) have opened an investigation into the incident.
The LFP have worked hard recently in an attempt to stamp racism out of French football, following an incident last month which saw Valenciennes captain Abdeslam Ouaddou racially abused by a Metz supporter.
Metz were on Thursday docked one league point and ordered to play a home match behind closed doors. A similar sanction could now be slapped on PSG.
Thiriez, the president of the LFP, said in a statement: 'What should have been a great celebration of football, of the brotherhood and union against racism and all forms of discrimination, has been in part ruined by a handful of imbeciles filled with hate - and that despite the security measures taken and the speed of our intervention immediately afterwards.
'The firmness of the league's reaction will be equal to the suffering it has brought to the image of our football.
'As far as disciplinary measures are concerned, the disciplinary commission has been overcome by the report of the match delegate of which I am aware and, believe me, the severity of which showed the seriousness it will be looked into by the league.
'As for judicial measures, the league is going to lodge a complaint with the civil constitution for the incitement of hatred and violence.
'Paris St Germain and Lens will join forces in this complaint.
'I hope that with the video surveillance on one hand and the list of names on the tickets on the other, the police will be in a position to identify those involved, arrest them and deliver justice to them.'
PSG released a statement on Sunday, in which they condemned 'this hurtful, coarse and clearly intolerable message'.
'The club offers its sympathy and deep respect to Lens Football Club, its president and all the Lens supporters,' the statement added.
'It is regrettable once again that a minority of so-called supporters darken the image of the true supporters and PSG sympathisers in particular, and all lovers of football in general.'
PSG's fans have earned a bad reputation as a result of a number of shameful incidents over the past few years.
A section of supporters dubbed 'The Boulogne Boys', who dominate the Boulogne Kop at one end of the Parc des Princes, have generally been at the forefront of any violent or racist acts.
In November 2006, a PSG supporter was killed accidentally by a policemen who had come to the aid of a Hapoel Tel Aviv fan being hounded by a band of PSG followers, following a UEFA Cup match between the two teams.
This season, a section of PSG fans have caused trouble before and after Ligue 1 games at Nice and Marseille.
A points deduction would plunge PSG even closer to relegation from the top flight.
After the weekend's games, the capital club are second from bottom, two points from safety.
They do have a game in hand over most of their bottom-of-the-table rivals, however.
• Meanwhile, French President Nicolas Sarkozy has called for tough sanctions after a racist banner was unfolded by Paris St Germain supporters.
'The president wishes that this intolerable behaviour will have the follow-up it deserves and will follow with great attention how the investigation progresses,' read a statement issued by Sarkozy's office on Monday.
The banner referred to a film about the life of the Ch'tis, a nickname for the people of northern France, which is breaking box office records in France. It read: 'Paedophiles, unemployed, inbred: welcome chez les Ch'tis.' The banner was unfolded briefly at the start of the second half of the game between PSG and northern club Racing Lens at the Stade de France.
Sarkozy, who was at the match and asked for the banner to be removed, will meet Lens mayor Guy Delcourt and Racing Lens officials on Tuesday.
Delcourt has asked for the final, won 2-1 by PSG after a controversial late penalty, to be replayed.
French prosecutors have asked police to try to identify the supporters involved, who could face jail sentences of up to a year.
The French football league (LFP) launched its own inquiry on Sunday. Its disciplinary committee will meet on Thursday to study the incident.
A replay is unlikely but PSG, second from bottom in the Ligue 1 standings and threatened by relegation, could be docked points.