British Transport Police (BTP) are keen to speak to the man, pictured above, in connection with the incident, which took place at 5pm on Saturday, May 15.
Police constable Omid Aslanbeigi said: “The victim, a 22-year-old member of station staff from Leeds was checking tickets at the barrier when a man attempted to pass through with an out of date ticket.
“When he challenged the man he was grabbed and punched in the face, causing him to fall to the floor.
“The victim was left with bruising to his face.
“This was completely unacceptable and deplorable behaviour.”
Anyone with information can call BTP on 0800 40 50 40 or Crimestoppers on 0800 555 111.