Rail passengers will see ticket prices rise on average by 3.5% next year after official inflation figures used to calculate increases were published - sparking commuter protests.

The Retail Prices Index (RPI) measure of inflation for July was 2.5%, down from 2.6% in June, the Office for National Statistics (ONS) said.

Regulated fares, which include season tickets, can rise by RPI plus 1%. The hike for 2015 will be marginally lower than it was this year.

However, it led to protests across the country today - including at Whitstable this morning.

Michael Roberts, chief of the Rail Delivery Group, which represents train companies including Southeastern and Southern, said: “Money from fares pays for more trains, better stations and faster services on what is already Europe’s fastest growing, safest and most improved railway.

"Over the next five years, £38bn will be invested in improving the network.”

He added: “Government decides the average change to regulated fares, including Season tickets, each year.

"For a decade, successive governments have regulated commuter fares so as to increase the share of rail’s costs paid by passengers rather than taxpayers.”

Commuter groups criticised the increase.

Martin Abrams, of the Campaign for Better Transport, said: “With people’s wages stagnating, and in some cases falling, the expense of taking the train to work has become a huge part of living costs.

"If the government doesn’t put an end to above-inflation fare increases quickly, ordinary commuters will be priced off the train and could be forced into agonising decisions such as moving house or quitting their jobs.”

The formula also allows train companies to raise regulated fares by a further 2% under the flex rule.

Kent commuters were faced with a 2.8% increase this year - actually much less than originally feared.

The increase was originally set at July’s Retail Price Index (RPI) plus 1%, but Chancellor George Osborne last month took away the 1%, leaving the rise at an average of 3.1%.

Southeastern went a step further and pegged it at an average of 2.8%.

With an election looming, the government could be looking for ways to spare rail travellers being stung by large hikes in season tickets.

A 3.5% increase would see the price of a travelcard season ticket from Ashford to London, which includes High Speed One, rise by £206 to £6,119.

The cost of a standard season ticket, which excludes High Speed One services, would increase by £195 to £5,754.

For a season ticket excluding use of the underground, the cost would increase by £178 to £5,102.

Ashford MP Damian Green said he would be urging the Chancellor to drop the additional 1% on fares as happened this year and said the era of inflation-beating hikes needed to come to an end.

He said: "The era of above-inflation rises needs to come to an end. Rail travellers are being stretched to their limits. Higher fares ought to be accompanied by more reliable services.

"Services that are unreliable are not acceptable. I do think people are more willing to pay for premium services like High Speed One because it is reliable."

He also urged Southeastern to consider pegging back the increase as it did this year, when it chose to increase regulated fares by 2.8%.