A 23-year-old man was almost sexually assaulted twice by the same unknown male, inside a Melbourne city shopping centre toilet cubicle earlier in the year.

Police have been told the 23-year-old went into the toilets at a La Trobe Street shopping centre about 4pm February 6.

Police released this image of a man that may assist with inquiries into a sexual assault in Melbourne.

He walked into the toilets, where an unknown man tried to push his way into the victim's toilet cubicle.

Police said when the victim tried to leave the toilet, he was sexually assaulted by the man.