The last thing Derek Hanekom expected when he tweeted about a "filthier" Johannesburg was an avalanche of clapbacks from Twitter, but that's exactly what he got.

On Wednesday, Hanekom tweeted a photo of a dirty Johannesburg street corner with the caption addressed to city mayor Herman Mashaba.

Hanekom wrote: "@HermanMashaba you promised so much, but parts of the city are filthier than ever before. Not good. This is a basic municipal function."