Police have released an image of a man they want to speak to over a string of alleged sexual assaults on trams in Melbourne’s CBD.

Detectives said they believe the same man may have committed the assaults over the past 12 months.

In each incident, a man allegedly approached the victim before inappropriately touching them and leaving.

Police received a report of one assault on the route 109 tram on Collins Street shortly after 5:30pm on April 16, 2016.

Police released an image of a man they want to speak to about the alleged assaults. Photo: Police Victoria

Two assaults were reported on the route 96 tram on Bourke Street: near Russell Street, shortly after 1:35pm on August 16, 2016; and on Nicholson Street, near Parliament station at 5:45pm on April 26 this year.

Another assault was reported on the route 1 tram on Swanston Street, near Little Bourke Street, shortly after 8:50pm on March 16 this year.

The man is said to be of Caucasian appearance, at least 180cm tall with a medium build, grey curly hair and glasses.

Anyone with information has been urged to contact Crime Stoppers.