The far right lawmaker's Vlaams Belang party is campaigning for the general election using the slogan "Your stick behind the door". Mr Dewinter now intends to file a complaint with the judicial authorities.
It is believed that the figure is the work of the Nawas graffiti crew.
Mr Dewinter told VRT News: "I'm filing a complaint against persons unknown for vandalism. This is damage inflicted on public property. It's just not done. In addition it's insulting and our campaign is being abused. It must be made clear that I am in no way linked to this."