Media playback is unsupported on your device Media caption Commuters react as rail fare rises take effect: "It's gone up every year, relentlessly"

Average rail ticket prices have risen by 3.4% across the UK, in the biggest increase to fares since 2013.

Many commuters have seen their season tickets go up by more than £100, while campaigners and unions warn many people were being "priced off" UK railways.

Andy McDonald, the shadow transport secretary, said the railway network was "fractured, expensive and complex".

The Department for Transport said price rises were capped in line with inflation and improved the network.

Commuter routes that are now more expensive include Liverpool to Manchester (up £108 to £3,152), Maidenhead to London (up £104 to £3,092) and Elgin to Inverness (up £100 to £2,904).

Media playback is unsupported on your device Media caption How do UK rail fares compare to Europe?

Fare increases to regulated fares - which comprise about half of all tickets - are calculated using the previous July's Retail Prices Index (RPI) measure of inflation.

Since 2007 the financial burden of running the rail system has increasingly fallen on passengers, after the government decided taxpayers as a whole should pay less via subsidies.

Conservative MP Martin Vickers, a member of Parliament's transport select committee, sympathised with season ticket holders, but told Radio 4's World at One programme that it is appropriate for rail passengers to make their contribution to the system.

"The reality is that someone has to pay and it's either the tax payer or the users of the system," he said.

He said the system of privatisation is "far from perfect" but added that it was the failings of Network Rail - which is nationalised - that is leading to the system's "lack of capacity".

Image copyright PA Image caption Campaigners have planned protests at busy rail stations, including Kings Cross in London

Fares used to account for about half the cost of running our trains, whereas now it is about 70%.

Paul Plummer, chief executive of industry trade body the Rail Delivery Group, said fare changes would provide cash for better services and investment, including the Thameslink and Great Northern rail upgrades.

Speaking from London Bridge station, where five revamped platforms have been opened, he said fares were "underpinning massively required investment".

Bruce Williamson, of campaign group Railfuture, says the lower Consumer Price Index (CPI) inflation measure should be used for regulated fare increases.

He argued that if CPI had been used rather than RPI since 2004, rail fares would be 17% lower.

Transport Secretary Chris Grayling is out of the country for a ministerial visit to Qatar, but a government spokesman said the way fares were calculated was "under review".

The spokesman said the government "carefully monitors how rail fares and average earnings change".

Labour's Mr McDonald said his plans to join protests across the country were "interrupted" after his train to Leeds broke down.

He tweeted a video message on board, saying: "Let's take our railway back into public ownership."

Passenger Sarah Beer, from Lingfield in Surrey, pays nearly £4,000 a year for her rail commute to London, which she describes as an "extortionate amount of money".

"It is like watching the Great Train Robbery all over again," she told BBC Radio 4's Today programme.

"What I cannot grasp, in this day and age, is that all we ask for is a reliable train service."

Robin Keenan, from Waltham Abbey in Essex, said he has been priced out of his London-based job due to ticket costs.

"I'm starting a new job tomorrow that's a lot closer to home - so no more trains," he told BBC News.

"I've taken a £2,000 hit in my wages but I'll be saving that amount due to a short bike journey."

Many commuters expressed their frustration with the increases on social media.

Stephen Joseph, chief executive of the Campaign for Better Transport (CBT), accused the government of choosing to "snub rail passengers" while fuel duty continued to be frozen.

"The extra money that season ticket holders will have to fork out this year is almost as much as drivers will save," Mr Joseph said.

London Mayor Sadiq Khan, who has frozen fares across the capital's TfL network until 2020, questioned why ticket prices were going up elsewhere.

"It's a scandal that the government are allowing failing private train companies to increase rail fares again," he said.

Meanwhile, Mick Cash, general secretary of the Rail, Maritime and Transport Workers (RMT) union, warned people were being "priced off" UK railways.

He told BBC News that public ownership of the railways was a "necessary" step.

The union has staged fare protests in stations across England and Wales, with separate protests planned for 3 January in Scotland where it is a bank holiday.

A spokesman for the Department for Transport said it was investing in the "biggest modernisation of our railways since the Victorian times".

He said: "This includes the first trains running though London on the Crossrail project, an entirely new Thameslink rail service, and continuing work on the transformative Great North Rail Project."

Mark Carne, chief executive of Network Rail, said passengers would see a "huge change" in the coming year due to investment in rail networks.

"We all share the desire to try to keep fares as low as possible," he told BBC Breakfast.

"My job is to run the network as efficiently as possible."