CCTV footage has been released after a man allegedly touched himself in front of a 15-year-old girl on a tram last month.

Police say the incident happened on a St Kilda-bound tram on Clarendon Street around 7.15pm on Sunday, June 19.

Shortly after getting on the tram, the man sat about a metre away from the victim and began touching himself while staring at her. 

The victim became uncomfortable and moved to the other end of the tram.

The man is thought to be aged in his mid-50s, unshaven and was wearing a distinctive blue and orange beanie.