The Dutch Football Association (KNVB) have condemned the actions of an Ajax fan caught on camera pretending to lynch the club's former player and current Feyenoord goalkeeper Kenneth Vermeer at Sunday's match.

Pictures shared on social media after the game show an Ajax supporter hanging by the neck an effigy of Kenneth Vermeer, with the plastic mannequin wearing a t-shirt with the Vermeer's name and Feyenoord number.

In an interview KNVB director of professional football Bert van Oostveen described the incident as "appalling" and "unacceptable" and called on supporters’ associations to step up their efforts to combat improper behaviour.

"We’re all talking about a scandal. Today we saw 50,000 people stand by and watch as somebody walk in with an effigy,

"That’s why I want to talk to supporters’ associations about how we can turn this around. We have a collective responsibility." he said.

The 30-year-old Dutch international was also the target of hostile chanting during the match, leading to a stadium announcement to halt the abuse.

"I’ve seen and heard enough, but these things are on the fringes," Vermeer told after the game.

"You hear these things but you can’t let it distract you. What should I say about it? Not so much." he added.

The player filled a police complaint about the incident.

KNVB concerned over 'worsening atmosphere'
KNVB president Michael van Praag described the actions as "completely unacceptable" while Bert van Oostveen expressed his concerns over the worsening atmosphere at and around football matches in Dutch football.

In January Ajax defender Riechedly Bazoer was subject to monkey chants by a section of ADO Den Haag fans. Last weekend Feyenoord midfielder Marko Veijnovic received death threats at his home in front of his family.

Following the incident the Amsterdam club announced a stadium ban for the perpetrator, saying he now faces a criminal investigation.

Ajax manager Frank de Boer said the treatment of Vermeer was "very disappointing", adding that he is pleased with the stadium ban.

"He’s one of our former players who always gave 300 per cent for the club, since he was in the youth team. Support your own team instead of doing this." he said.

Feyenoord captain Dirk Kuijt said: "It’s a few idiots. They need to be banned and given as little attention as possible."