Former prime minister Kevin Rudd's godson has allegedly been attacked and verbally abused after attempting to stop a man removing banners supporting the "yes" vote in the same-sex marriage survey.

Sean Foster, 19, was allegedly assaulted by a man as he waited at a bus stop on Oxford Street in the Brisbane suburb of Bulimba about 9am on Tuesday.

The man, who was reportedly pulling down rainbow "Bulimba 4 Marriage Equality" flags at the time, is yet to be identified and Queensland Police are continuing their investigations.

However, Foster's godfather took to social media on Wednesday to upload a photo of his bloodied face, allegedly taken after the altercation.