Train companies escape paying compensation for over 30 million delayed passenger journeys each year, according to new research.
Consumer group Which? estimated that 47 million individual journeys were either cancelled or significantly late in the 12 months to March.
Most train companies offer compensation if services are delayed by at least half an hour, but a survey of 7,000 passengers found only a third (34%) of those who may be entitled to a payout actually made a claim.
This means some 31 million disrupted journeys do not result in a payout.
Which? has used its powers under the Enterprise Act 2002 to launched a super complaint over how the rail industry compensates passengers.
It has formally requested that the Office of Rail and Road (ORR) investigates the issue and called for the process of obtaining payouts to be simplified.
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 according to the Department for Transport (DfT), figures from 12 operators - including Virgin Trains, CrossCountry and Southern - show a total payout to passengers of just £26 million over the same period.
NR says the payments it makes to train companies compensates them for the "long-term impact of disruption" as it is thought delayed passengers will be less likely to travel by train in the future, which affects revenue from fares.
Richard Lloyd, executive director at Which?, said: "Current proposals to improve compensation for passengers are too far down the track.
"Even if an automatic compensation system was included in all new franchises from tomorrow, it would take until at least 2025 to cover the whole network.
"Millions of passengers are left out of pocket each year, so train companies must do more to put their passengers first and make rail refunds easier."
The consumer group carried out a mystery shopper exercise to ask "basic questions" on refunds at 102 train stations.
In just 18% of cases the person was given a "full explanation" of the conditions for claiming, while in 63% of visits they were not told they could request their compensation in non-voucher form, such as a cheque.
Virgin Trains recently launched automatic delay repay for some tickets, but this has not been introduced by other companies which still use paper or online forms.
A spokesman for the Rail Delivery Group (RDG), which represents train operators and NR, claimed compensation has become "increasingly generous and easy to apply for".
It insisted that train companies are doing "lots more" to inform passengers of their entitlement to a payout with announcements on trains, handing out claim forms, issuing email reminders and posting messages on Twitter.
A DfT spokeswoman said: "We are committed to improving compensation arrangements and it is happening."
Manuel Cortes, general secretary of the Transport Salaried Staffs' Association, which represents ticket office workers, commented: "It is the franchise operators who put profit before the public. It is not our members who are failing in their duty of care to passengers and swindling them of their money."
Super complaints can be made by consumer groups when it appears the interests of customers are being significantly harmed. The ORR is required to respond to Which? within 90 days.