Anti-racism campaigners have called on Unesco to remove a Belgian folklore festival from its cultural heritage list unless organisers stop parading characters in blackface.

The four-day carnival in the Belgian town of Ath, which gets under way on Friday, will feature “the savage”, a white man in blackface, who wears a chain around his neck and a ring through his nose. According to the official festival website, “the ‘savage’, chained and agitated, testifies to the taste for the exotic of the 19th century”.

In a letter to Unesco, an anti-racist group, the Brussels Panthers, said the character was “adorned with all the humiliating signs that our racist societies have projected on to black people throughout history”.

The letter, co-signed by 13 other anti-racism groups, as well as dozens of activists and academics across Europe, describes blackface at Ath and other folkloric events as “acts of symbolic violence towards the black communities of Belgium – acts that are mirrored by the acts of real physical violence and material discrimination that the same communities also encounter”.

Mouhad Reghif, spokesman for the Brussels Panthers, told the Guardian that blackface had very serious consequences on the daily lives of black people in Belgium and elsewhere in Europe.

Reghif, who has received dozens of threatening messages since launching the campaign, said blackface helped preserve discrimination and racist attitudes.

“There remains the attitudes of the 1950s and 60s that Belgium brought civilisation to the Congo [its former colony] and colonialism was something good. With this we maintain negrophobia and white supremacy that was born in colonial times.”

The “savage” character appears on one of 22 floats that process through the small town of Ath on the last Sunday of August. The carnival also usually includes a blackface devil character, dressed in black cloak with red horns.

Less controversial figures include David and Goliath, and a giant horse, carried by 16 people.

The centuries-old festival traces its roots to a late medieval parade to consecrate a church, but the savage character did not appear until 1873. The event was listed as part of the “intangible cultural heritage of humanity” by Unesco, the UN’s cultural agency, in 2005, along with other folklore parades involving dragons and giants in Belgium and France.

Laurent Dubuisson, a historian who runs Ath’s House of Giants museum, which houses models and costumes, rejected the charge of racism.

“The whole town, they have been a little surprised by the polemic, because this personage, the savage, is the most popular. This character is a real star of the Ath festival.”

In an interview he said there was “huge affection” for the savage character, who typically embraces festival-goers, leaving black marks on their faces.

“The makeup has enormous importance, it is a mark of affection,” he said. “To end blackface breaks a little how this [ritual] works.”

The blackface characters, he said, were unchanged since the Ath festival was inscribed on the Unesco heritage list in 2005. “The devil and the savage are part of the heritage, in the same way that in a Catholic church, or a museum, you can see works of art of art created 200, 300 or 500 years ago that are shocking for our current mentality.”

Campaigners say they do not want to stop people enjoying themselves, but are asking organisers to think again about blackface. “The intangible heritage of humanity, the Ducasse [Ath parade] belongs to us as well,” Reghif told Le Soir. “Certainly less than the Athois, but as much as the rest of the Belgian population, of humanity, which we are part of.”