A man is in a serious condition in hospital after he was hit by a moving train following a "wrestle" with Protective Services Officers at Preston railway station on Monday night.

The man is believed to have leapt down onto the tracks between the platforms to escape PSOs in the moments before he was struck and took a heavy blow to the head.

According to an internal Metro report seen by The Age, the "unidentified male [was] pursued by PSO, [and] struck side of departing train".

Ambulance Victoria said the man, aged in his 30s, was taken to the Royal Melbourne Hospital in a critical condition with head injuries.