Compensation arrangements for delayed train journeys should be standardised across the entire rail network, according to a demand by passenger groups.
Currently arrangements vary depending on the rail operator, and many passengers who may be entitled to compensation never make a claim.
Operators apply different rules for compensation claims.
A scheme for East Midlands Trains comes into effect after a 30-minute delay, but Great Western's high-speed services must be at least an hour late to warrant compensation.
Similarly, passengers with a single ticket on First TransPennine Express can get compensation worth 100 per cent of the fare if they are delayed by 30 minutes, while the same disruption on Arriva Trains Wales is only worth 20 per cent.
Martin Abrams, public transport campaigner at the Campaign for Better Transport, said there was an "urgent need to improve consistency and clarity".
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Train companies themselves receive payouts for unplanned delays that are attributed to Network Rail.
But research by consumer group Which? found that train companies escape paying compensation for over 30 million delayed passenger journeys each year.
A study by campaign group Passenger Focus, released in 2013, found that 88 per cent of passengers who may be eligible for a pay-out do not claim.
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".
He also said operators 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.