A man was kicked in his stomach after asking another man to stop bothering passengers at Doncaster railway station.
He was attacked in the travel centre after confronting the man.
PC Kevin Challinor, of British Transport Police, said: “The victim was standing in a queue at the travel centre waiting to purchase a ticket.
"He asked a man who was being verbally abusive and swearing at other customers to stop.
“The man reacted by lashing out and kicking the victim in the stomach.
“Quite understandably the victim was left shocked by this attack. No-one should be made to feel uncomfortable, intimated or concerned for their safety in this way, it is simply not acceptable.”
Officers investigating the incident at 8pm on Friday, June 3 have released a CCTV image of a man they believe may hold vital information
CAll British Transport Police on 0800 40 50 40 or Crimestoppers on 0800 555 111.