A group of Chelsea thugs prevented a black man getting on to a train in Paris before chanting: "We're racist and that's the way we like it."
Footage posted online shows the football fans shouting and gesturing at the man before pushing him out of the carriage when he steps in.
The supporters are thought to have been travelling to the Parc des Princes ground for Chelsea's Champions League match against Paris St Germain on Tuesday night, which ended in a 1-1 draw.
They also chanted at bemused onlookers: "Where were you in World War Two?"
Chelsea released a statement condemning the incident and said it will take action if members are found to be involved.
"Such behaviour is abhorrent and has no place in football or society," the club said.
"We will support any criminal action against those involved, and should evidence point to involvement of Chelsea season-ticket holders or members, the club will take the strongest possible action against them, including banning orders."
Paul Nolan, a British expat who filmed the incident on his phone, said the train had been stopped for around three minutes when the man arrived on the platform and tried to get on.
Mr Nolan told the Guardian: "He was obviously completely shocked when they pushed him off. I don't think he realised who they were. He then tried to get on again and got pushed off a second time.
"I was just completely appalled by it and so that's why I tried to catch some of it on my phone, although I was a bit self-conscious as it was getting quite aggressive and I overhead one of the Chelsea fans say something about stabbing someone. I think he was referring to a Paris St Germain supporter who was on the platform."
Chelsea fanzine editor David Johnstone believes the incident could have severe consequences for the club's reputation.
"Because of the actions of possibly half a dozen people on a Metro train in Paris, all the supporters are going to be labelled as racist," he told BBC Radio Five Live.
"I think the majority of Chelsea supporters are disgusted by what's happened. The 2,000 who were in Paris today support a Jewish-owned football team where the majority of players are black and foreign."