The victim, who has not been named, was travelling on the 11.39pm train from London Liverpool Street to Shoeburyness in Essex with his partner on 14 April when he was confronted by a group who began making homophobic comments.
As the journey progressed the hateful speech became more severe, with one saying that “gays should be strung up”.
When the victim attempted to leave the train at Upminster station in east London he was repeatedly punched in the head, and collapsed onto the platform where he was left unconscious for several minutes.
Detectives have released images of three men they are seeking in connection with the incident.
In a statement British Transport Police said: “Officers believe the men shown in this CCTV images may have information which could help them investigate.
“No one should ever be targeted with abuse or violent because of who they are, or who they love.
“We take all reports of hate crime seriously and will work hard to identify perpetrators and bring them before the courts.”
If you have any information relating to the incident you can contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 58 of 14/04/2019. Or you can ring Crimestoppers anonymously on 0800 55 111.