Photo: abc.net.au

It is believed the victim left a venue on Lonsdale Street about 1am on 29 April and was assaulted as he walked home.

Investigators have been told the 32-year-old man suffered serious injuries as a result of the assault.

Investigators have released an image of a woman who is believed to have left the venue with the victim and who witnessed the assault. Police are encouraging her to come forward.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.