Some rail firms have already reported job losses and service cuts
Rail unions have warned rail firms may try to save money during the downturn by cutting services and have pledged to fight any attempts to do so.
Their concerns come as the five largest public transport firms meet Transport Secretary Geoff Hoon, with the economic impact on the agenda.
The Rail Maritime and Transport union (RMT) said firms have made vast profits and must not be allowed to make cuts.
A representative of train operators said the talks were "routine".
RMT General Secretary Bob Crow said rail firms had received huge subsidies from the government and continually raised fares for passengers by 1% above inflation, but now at the prospect of a dip in profits wanted to cut jobs and services.
Mr Crow said when rail workers ask for similar pay increases they are told their demands are unsustainable.
He said: "It's like walking into the bookmakers and putting £10 on a horse at Epsom this afternoon, but then when the horse loses asking for the £10 back.
"What we should be encouraging is more people out of their cars onto the railway network and if you cut services then you won't get people out of their cars."
Earlier, Mr Crow described the rail operators as "greedy privateers" who wanted "to have their cake and eat it" and who had made "tens of millions of pounds" from "public subsidy, overcrowding and massive fares hikes".
He said: "Revenues, profits and dividends have been rising steadily, but at the first hint of a slowdown they want to slash services and sack staff when that is the reverse of what the economy and environment need."
The Association of Train Operating Companies (Atoc) declined an offer to speak to the BBC, but earlier a representative said the meeting between Mr Hoon and Stagecoach, National Express, Go-Ahead, Arriva and FirstGroup, was nothing out of the ordinary.
He added: "Some off-peak trains may be reduced in length, but I don't think anyone at this stage is talking about service cuts."
Some rail firms have already reported the economic slump has forced them to cut jobs and services.