A sexual predator responsible for a number of assaults on Melbourne's trams over the past year is being hunted by police.

It's believed the man sexually assaulted women on four separate occasions on popular tram routes as they travelled through the CBD.

An image of the man police wish to speak to over assaults on trams in the Melbourne CBD.

In each incident the man approached the victim and inappropriately touched them before leaving the tram. A number of assaults occurred during the evening peak-hour commute.

The first assault took place on the route 109 Box Hill tram on Collins Street about 5.30pm on April 16 last year.