Rail commuters face the prospect of a hike of at least 5.8% in the price of season tickets in the new year following Tuesday's announcement of inflation figures.
The increase could be even more if, as some fear, the Government scraps the current annual price-rise formula.
Under the existing formula, train companies are allowed to raise regulated fares annually, which include season tickets, by 1% above whatever the previous July's retail price index (RPI) inflation figure is. The RPI figure for July was 4.8%, which would mean a 5.8% fares rise in January 2011.
Transport Secretary Philip Hammond has said that he is not in a position to say whether the current RPI plus 1% formula will remain, meaning that fares could rise in excess of the 5.8% figure.
Ashwin Kumar, rail director of train customer watchdog Passenger Focus, said: "Passengers continue to tell us their top priority for improvement on the railway is better value for money.
"With the whole country feeling nervous about our economic prospects, passengers will expect train companies to show restraint next January. Now is not the time for train companies to sweat passengers off the train."
Passenger Focus said it would also like to see continue the policy of limiting the flexibility of train companies to increase fares on individual routes.
Mr Kumar went on: "In the past, the average fare rise has masked increases on some routes of 10 or 11%. We hope the Government continues to limit train companies' flexibility so passengers on some routes don't face double digit rises.
"Our research has shown that passengers in Britain already pay some of the highest commuter fares in Europe. For example, an annual season ticket for a journey such as Warrington to Manchester costs 60% more than an equivalent journey into Paris. Just because you can increase fares, does not mean you should - this is a time for restraint."
Bob Crow, general secretary of the Rail Maritime and Transport union, said: "With fares expected to be jacked up through the roof in January there is no doubt that this Government is hell bent on ring-fencing the profits of the private operators while forcing passengers to pay through the nose to travel on over-crowded, under-resourced and unsafe services."