Train fares could surge by as much as 5.8 per cent as new RPI figures were released by the Office for National Statistics.
The figures, released this morning, show the Retail Price Index (RPI) was 4.8 per cent higher than a year ago.
In England, the price of certain regulated rail fares - things like season tickets, and some on/off-peak tickets - are typically determined by the RPI.
Therefore, a rise in the RPI tends to mean train prices follow suit.
Last year, the RPI increased by 3.6 per cent and rail costs were then raised by 4.6 per cent.
Experts are predicting that, if this year follows the same trend and the increase is one percentage point more than the newly announced RPI of 4.8 per cent, the price of train tickets could be increased by 5.8 per cent.
Bruce Williamson, spokesman for pressure group Railfuture, described the hike as "outrageous".
He said: "What would be the justification for jacking up fares above inflation? There isn’t any.
A spokesman for the Transport Secretary said 'no decisions have been made on next year’s rail fares'
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"It’s ripping off the customer, driving people off the trains and onto our congested road network, which is in no one’s interest."
Although the Government, which is responsible for determining the price cap on rail costs, has yet to confirm the price hike, a spokesman from the Department for Transport said: "The Transport Secretary has made clear her number one priority is getting the railways back to a place where people can rely on them.
"The Government is putting passengers at the heart of its plans for public ownership and Great British Railways, delivering the services they deserve and driving growth.
"No decisions have been made on next year’s rail fares but our aim is that prices balance affordability for both passengers and taxpayers."
Some commuters could face rises of above £2,000
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Liberal Democrat Transport Spokesperson Paul Kohler MP has warned the Government that passengers are being "taken for a ride".
In a statement this morning, the Liberal Democrats called for rail fares to be frozen to avoid another hit to the cost of living and encourage more people to use trains.
According to research by Ed Davey's party, some commuters could face rises of above £2,000 since 2020.
In layman's terms, this means a season ticket from Winchester to London will cost £6,984, up by £256 from last year, and £226 more from Cambridge.
The Wimbledon MP said: "This is nothing short of ludicrous.
"Commuters are simply being taken for a ride. We simply cannot allow the current rate of inflation to set rail fares while services get worse.
"To increase rail fares at all in the midst of a cost-of-living crisis would be nothing other than a slap in the face to ordinary people.
"The Liberal Democrats are calling on the Government to scrap the 2026-27 rail fare rise and get more people onto the trains.
"Raising fares is a false economy that will only drive down passengers and revenue in the long run."