Two thirds of Britain's rail operators are owned by overseas companies, leaving passengers paying high fares to boost the profits of foreign firms, according to a new report.
The Rail Maritime and Transport union said state railways in Germany, France and Belgium were among those running rail services in this country.
The union said its research, released at its annual conference in Brighton, made a "mockery" of the Government's policy on railways.
An East Coast train waits on the platform at London's Kings Cross Station
The union has been campaigning against a decision to re-privatise the East Coast mainline.
General secretary Bob Crow said: "This research blows apart the whole government case for bulldozing through the early re-privatisation of the East Coast mainline.
"What they are actually saying is that any state can run our railways as long as it isn't the British state.
"The hard truth is that the British public are paying the highest fares in Europe to travel on crowded and ageing trains in order to subsidise railways in Germany and other parts of the Continent.
"RMT stands shoulder to shoulder with our European colleagues fighting to keep their railways in public hands but what a nonsense it is that our own Government is denying us the same benefits of lower costs and increased investment that the public ownership so clearly brings."