Rail fares are set to rise by 3.6% in January in line with the Retail Price Index (RPI) figure for July.
The government uses July’s RPI figure to set the amount at which regulated rail fares will increase the following January.
Last month’s figure is the highest July figure since 2011, when it was 5%.
Regulated fares in England and Wales include ‘anytime’ and some off-peak fares, and season tickets.
In Scotland, annual increases for off-peak fares are capped at RPI minus 1%. Peak fares including anytime and season tickets can rise by the level of the RPI.
Unregulated fares such as super off-peak travel and advance tickets will be set in December.
Transport Focus, the independent transport user watchdog, pointed to low levels of satisfaction among rail passengers.
“Commuters do not give value for money on their railways a high satisfaction score – just one third according to our latest survey.
“So while performance remains patchy and with pay and wages not keeping pace with inflation, they will feel rightly aggrieved if they are paying much higher rises next January.”
Mr Sidebottom also questioned the government’s continued use of RPI to determine price increases.
“Why is the Government not using its preferred measure of inflation: the one that is used to determine wages and pension increases, and one which is often lower than RPI? Why not use the Consumer Prices Index for rail fares too? Passengers deserve a fairer deal.”
Paul Plummer, chief executive of the Rail Delivery Group, said: “Money from fares pays to run and improve the railway, making journeys better, boosting the economy, creating skilled jobs and supporting communities across Britain, and politicians set increases to season tickets.
“It’s also the case that many major rail industry costs rise directly in line with RPI. Rail companies are working together to improve performance now, adding thousands more seats over the next 18 months and, longer term, simplifying fares and ticket buying so that the country has the railway it needs to prosper.”
Last week, the Department for Transport announced a £1bn investment in services on the West Midlands rail network.
The deal with West Midlands Trains Ltd will see 400 new carriages rolled out by 2021, making space for an extra 85,000 passengers on rush hour services between Birmingham and London.
Passengers will be able to access free wi-fi on all main line services by the end of 2019 and get compensation if services are delayed by more than 15 minutes.
There will also be improved access for those needing extra assistance, including disabled people.
Transport secretary Chris Grayling said: “We are improving the whole travelling experience with live train crowding information, compensation for people delayed by 15 minutes or more, smart ticketing and better value tickets for part-time workers.
“This shows we are delivering on our commitment to build a railway that works for everyone.”