One train guard said the abuse hurled by two men towards other passengers on a train from Liverpool Lime Street to Wigan Wallgate was "the worst she'd heard in a long time".
British Transport Police (BTP) says the pair were each carrying bottles of beer and appeared to be drunk.
Investigators say the pair had boarded at Lime Street before they began racially abusing a male passenger.
The sustained and threatening abuse caused a female train guard to intervene, according to police
She told officers later that she hadn’t heard such abusive language in a long time.
The men then apparently became suspicious that the police had been called and got off the train at Prescot, before getting a taxi to St Helens.
The incident occurred at around 12.50pm on Friday, December 15, but details have only just been released by police, alongside CCTV stills of the suspects.
A BTP spokesman said: "Hate crime will not ever be tolerated. Officers would like to speak to the men in these images, as they believe they may have information which could help the investigation.
People with any information are being asked to call the BTP on 0800 40 50 40 or text 61016 with reference 284 of December 15.