Half of all passenger journeys on Britain's rail network will be on services owned by foreign countries after the new South West Trains franchise starts.
The equivalent of 863 million such trips were made last year, which was 50% of total journeys, according to Press Association analysis of industry data.
Labour's shadow transport secretary Andy McDonald called for the railways to be renationalised as he claimed it is "ludicrous" that foreign government-owned firms are invited to run UK services "in their own interests" but the British state "is banned from doing so".
He said: "With promised upgrades delayed or cancelled, punctuality at its worst for a decade and fares up 27% since 2010, it's becoming increasingly difficult for the Tories to justify allowing private and foreign state-owned companies to take money out of the system, which should be used to improve services or hold fares down.
"When in public hands, the East Coast Mainline returned over £1 billion to the Treasury, kept fares down, had record passenger satisfaction and had excellent industrial relations. We should be building on that success."
East Coast services were operated by a company under the control of the Department for Transport for five years when franchise holder National Express pulled out in November 2009.
London Overground is the busiest rail company fully or partly owned by foreign countries or governments, with 188 million journeys.
It is 100% owned by Arriva, a subsidiary of German state-owned Deutsche Bahn.
Northern, part of the same firm, is the second busiest operator under foreign ownership with 106 million journeys last year.
The totals are based on the number of journeys made with each company according to Office of Rail and Road figures, and adjusted by what proportion the firms are owned overseas.
It was announced on Monday that Hong Kong company MTR will run South West Trains with First Group for seven years from August.
This followed the recent awarding of the c2c franchise, which runs from the City of London to Essex, to Italian state operator Trenitalia.
Punctuality on Britain's rail network is at its lowest point in over a decade. More than one in 10 (12.3%) trains failed to reach their destinations on time last year.
Mick Cash, general secretary of the Rail, Maritime and Transport union, said privatisation has failed passengers and left foreign state train operators "laughing all the way to the bank".
He went on: "The revelation that so many of the UK train operations are now partially or wholly owned by foreign states or their railways is nothing short of a national scandal.
"The case for public own?ership of UK rail to end this racket is now overwhelming."
The number of journeys being made on Britain's railways has more than doubled over the past two decades, from 846 million in 1997/8 to 1.72 billion in 2015/16.
Recent analysis by the Rail Delivery Group (RDG), representing train companies and Network Rail, found that 6,400 more train services will be running each week by 2021 due to the ongoing £50 billion investment in the network.
RDG chief executive Paul Plummer said: "Passengers and taxpayers have benefited from franchising, where rail companies from around the world bring new ideas and innovation to Britain's railway, and railways across the world still want to learn from our successes.
"Rail companies have worked together to transform Britain's railway, doubling the number of passengers and creating one of the world's safest railways.
"Under franchising, the railway has gone from costing taxpayers £2 billion a year in terms of day-to-day costs to contributing £200 million, money which helps to fund major rail upgrades."
A Department for Transport spokeswoman said: "Rail franchises are awarded through fair and open competition to the bidder offering the best deal for passengers and the taxpayer. We look for expertise and knowledge to build a better railway."
The Government is delivering the biggest rail modernisation programme for over a century which will improve journeys by providing "more seats, more of the services people want and modern stations," she added.