Rail fares have risen nearly three times faster than wages over the past five years, leaving commuters "seriously out of pocket", according to a new report.
A study by the Action for Rail campaign showed that season tickets and other regulated fares had increased by 25% since 2010, while average pay went up by 9%.
Government plans to cap annual rises in regulated fares will cost taxpayers around £700 million over the next five years, but bigger savings could be passed on to passengers if train services were run by the public sector, said the report.
Season tickets could be 10% cheaper by 2017 if routes coming up for tender were given to public sector organisations, it was claimed.
It comes as rail passengers find out how much they will pay for their fares from January with the release today of inflation figures for July. Next year's fares are expected to see some of the lowest increases for decades.
TUC general secretary Frances O'Grady said: "Rail fares have rocketed over the last five years, leaving many commuters seriously out of pocket.
"If ministers really want to help hard-pressed commuters, they need to return services to the public sector. This is a fair, more sustainable option and it would allow much bigger savings to be passed on to passengers. Introducing an arbitrary cap on fares is simply passing the bill on to taxpayers.
"The Government wants the public to subsidise train companies' profits and bear the cost of the fares cap."
Aslef general secretary Mick Whelan said: "Once more, those who claim they want to make work pay devalue that statement with continual, excessive and unreasonable increases in fares."
Mick Cash, leader of the Rail, Maritime and Transport union, said: "While train companies threaten to throw guards off their services and axe station staff who are essential for safety, turning the network into a paradise for criminals and yobs, they are milking the travelling public for all they can ?through extortionate fares.
"Every penny of the fare rip-off is sucked out of the system in fat company profits, while crucial rail maintenance and upgrade works are shelved for lack of funds. ?That's the price of two decades of rail privatisation and the whole rotten business needs to be swept away and replaced by a public railway under public control."
TSSA general secretary Manuel Cortes said: "We have the most expensive rail fares in Europe and they have risen by over 200% on the most popular routes since privatisation 20 years ago.
"We should follow the European example and run a publicly owned railway for the benefit of the travelling public, not the private rail firms."
Rail minister Claire Perry said: "We know rail fares put a strain on family finances. That's why today, for fares we can control, we are putting an end to inflation-busting fare increases.
"Thanks to our plans, next year's fares will see some of the lowest increases for decades. And with the economy growing steadily, for the first time in 10 years wage rises are likely to be larger than average fare increases.
"At the same time we are delivering the largest programme of investment since the Victorian era so that customers get better value for money."