Merseyside Police has released CCTV images of man officers would like to speak to in connection with a racially aggravated incident on a bus in Walton.
A woman passenger was subjected to comments about her ethnicity by a male passenger who was travelling with a child.
The incident happened on the Number 21 bus from Kirkby to Liverpool, as the vehicle reached County Road in Walton at 1.20pm on May 25.
The offender then assaulted a man who challenged him about his comments.
The assault victim sustained facial injuries during the assault and has been left upset following the incident.
Detective Constable Bob Hart, said: "Incidents of this kind, whereby victims are subjected to racial abuse, be it physically or verbally, will not be tolerated.
"We are investigating a number of lines of enquiry and are keen to speak to anyone with any information that could help our enquiries.
"I would like to reassure people that incidents of this type are rare."
Officers from Sigma, the Merseyside Police's dedicated hate crime investigation unit, are appealing to the man pictured, anyone who recognises him or anyone with information to get in touch.
Anyone with any information is asked to call 0151 777 4843 or Crimestoppers on 0800 555 111.
More top news
Jeremy Corbyn addressed allegations of bullying within the Labour Party as he launched his campaign to remain as leader in Salford.
Turning wetter and fresher on Sunday
Humid, dry and warm start to the weekend, but turning fresher and wetter on Sunday afternoon