Alarming new footage shows commentator Andrew Bolt being assaulted on the streets of Melbourne in what he says is an example of how dangerous the city has become for conservatives.

The video, posted on social media on Thursday morning, shows a hooded man approaching Bolt from behind and throwing a substance at his head, initiating a brawl in broad daylight on busy Lygon Street.

The ensuing scuffle sees Bolt pushed into a pole and then falling over chairs and tables outside a restaurant. He fights back fiercely, kicking and punching his two assailants in the face and groin before they give up and start to walk away.

An unknown man shouts "what are you doing?" and "go away" as the brawl concludes.