Rail commuters are being warned to expect a 3.5% fare increase next year.

This would increase the annual cost of getting to work for many long-distance travellers by more than £150.

The exact fare rise will be confirmed when the July Retail Prices Index (RPI) measure of inflation is released by the Office for National Statistics on Wednesday.

But economists from Investec and EY Item Club both predict the figure will be announced as 3.5%.

The Department for Transport (DfT) uses July’s RPI to determine the annual increase in regulated train fares, which comes into force every January.

Regulated fares include season tickets on most commuter routes, some off-peak return tickets on long distance journeys and Anytime tickets around major cities.

These fares went up by 3.6% this year.

In January the governor of the Bank of England, Mark Carney, said RPI has “no merit”, adding that “virtually everyone recognises” the alternative Consumer Prices Index (CPI).

Rail campaigners want CPI to be used to determine regulated fare increases, as it is generally lower than RPI.

The introduction of a new timetable caused widespread chaos in the north of England and on various London commuter lines. Thousands of passengers are still waiting to receive enhanced compensation.

The disruption led to the Government vetoing further timetable changes expected in December, which means upgrades in areas such as the West Midlands, the west of England and South Western Railway routes have been cancelled or delayed indefinitely.

A Campaign for Better Transport spokesman urged the Government to “commit to a fares freeze”.

He said: “Given the mess surrounding the new timetable, the lack of improvements and the failure to deliver compensation, the Government cannot go on telling passengers that fare increases are justified.”

Manuel Cortes, general secretary of the Transport Salaried Staffs’ Association, told the Press Association that services are in “free fall”.

He said: “Justice for passengers means dropping the annual rip-off rise and also simplifying the Byzantine fare structure which privatisation has imposed.

“Better still, end this costly farce. Put passengers before profits by bringing our railways back into public ownership.”

And Labour’s shadow transport secretary Andy McDonald said: “Chris Grayling’s handling of our railways is now beyond a joke.

“The Government’s failure means passengers have faced truly staggering fare rises, with fares having increased three times as much as wages.

“Labour is calling on the Government to freeze rail fares on the routes most severely affected by the timetable changes – Govia Thameslink, Arriva Rail North and First Transpennine Express – as a small gesture of goodwill towards those passengers who have suffered and continue to suffer the worst of the timetabling chaos.”

The rail industry has pledged to remove jargon from tickets and journey information for half a million train routes next month.

A DfT spokesman said: “Any fare increase is unwelcome, but it is not fair to ask people who do not use trains to pay more for those who do.

“Taxpayers already subsidise the network by more than £4 billion a year – meaning that 38% of our transport budget is spent on the 2% of journeys that the railway accounts for.”

He added that fare increases are helping to pay for extra carriages and services, as well as upgrades on the Great Western Main Line and the Transpennine route.

Paul Plummer, chief executive of the Rail Delivery Group, representing train companies, said: “Of every pound spent on train fares, 98p is invested back into the railway, helping to underpin a once-in-a-generation investment to change and improve for the benefit of our customers, local communities and UK economy.”

Mick Cash, general secretary of the Rail, Maritime and Transport union, said: “This is another kick in the teeth for Britain’s passengers who are being robbed blind by greedy train operators for travelling in rammed out and unreliable services while the shareholders are laughing all the way to the bank.

“The continuing scandal on Northern Rail is just one example of what’s wrong and the only serious solution is public ownership.”

A Scottish Government spokesman said: “ScotRail’s fares increases are generally lower, on average, than those elsewhere in the UK.

“This is a result of our policy to place a cap that is lower than RPI on regulated off-peak fares increases, whereas the UK Government applies an increase at the level of RPI to all regulated fares.”