Compensation arrangements for delayed train journeys should be standardised across the entire network to make it easier to claim, according to passenger groups.
They have highlighted the difference between operators on when travellers are entitled to a payout, how they obtain it and what they receive.
Martin Abrams, public transport campaigner at the Campaign for Better Transport, warned that there was an "urgent need to improve consistency and clarity".
Passengers with a single ticket on First TransPennine Express can get compensation worth 100% of the fare if they are delayed by 30 minutes, whereas the same disruption on Arriva Trains Wales is only worth 20%.
The compensation scheme for East Midlands Trains comes into effect after a 30-minute hold-up, but Great Western's high-speed services must be at least an hour late to warrant compensation.
Mr Abrams told the Press Association: "We want to see an end to vouchers as a form of reimbursement, agreed targets for compensation being paid out, a single set of compensation arrangements across all passenger services and a timetable for automatic delay repay across the network."
He made the comment ahead of the average increase in Britain's train fares of 1.1% from January 2.
The latest Network Rail punctuality figures show 10.5% of services did not arrive at their final destination on time in the past 12 months.
Virgin Trains launched automatic delay repay for some tickets in October, but other companies are still using paper or online claim forms.
Transport watchdog London TravelWatch has raised concerns with Southern - which operates services between the capital and Sussex, Hampshire, Surrey and Kent - over "complexity issues and difficulties that passengers might experience" with the compensation form on its website.
Recent changes require passengers to complete an anti-spam test and fill in a tick box before their application is accepted.
More than one in four (26%) of its services were at least five minutes late between October 18 and November 14, according to punctuality figures published by Southern, which is part of the Govia Thameslink Railway (GTR) operator.
A GTR spokesman insisted that claiming compensation has been made easier in recent years and said the amount it pays to delayed season ticket holders will increase by 8% from January 2.
He added: "The minor changes recently introduced to the website are simply standard measures taken by websites to combat online fraud."
The Campaign for Better Transport claimed it is "imperative" the Consumer Rights Act, which came into force last month, is applied to rail delays because "only then will passengers' faith in the compensation scheme be restored".
But the Department for Transport (DfT) published a consultation on the issue which warned that any increase in costs through more compensation pay outs "is likely to be passed on either to customers through increased fares, or to tax payers".
Earlier this month consumer group Which? released research which found that train companies escape paying compensation for over 30 million delayed passenger journeys each year.
Meanwhile a 2013 study by independent campaign group Passenger Focus found that 88% of passengers who may be eligible for a pay-out do not claim.
Train companies received £106 million in 2014/15 for unplanned delays attributed to Network Rail (NR), such as those caused by infrastructure faults, vandalism and bad weather.
But DfT figures from 12 operators - including Virgin Trains, CrossCountry and Abellio Greater Anglia - show a total payout to passengers of just £26 million over the same period.
NR says the payments it makes to train companies compensate them for the "long-term impact of disruption" because of fears that delayed passengers will be less likely to travel by train in the future, meaning a loss of revenue from fares.
A spokesman for the Rail Delivery Group (RDG), which represents train operators and NR, insisted that passenger compensation pay-outs are increasing and it is becoming easier to claim.
He added that operators often pay compensation "regardless of what caused the delay" and claimed they are doing ''much more'' to inform passengers of what they are entitled to through more announcements on trains, handing out claim forms and posting messages on social media.
A DfT spokesman said it is ensuring that all new rail franchises make the claims process "swift and simple for everyone".
He added that the continued rolling out of the delay repay scheme would provide "a consistent way to claim".
Automatic compensation comes into effect for smartcard holders on c2c - which operates in the Essex and east London area - early next year, while the recently awarded Northern and TransPennine Express franchises will do this for Advance tickets bought online.