A survey of passengers and focus groups revealed that over 75% of passengers "do not know very much" or "nothing at all" about their entitlement when services are disrupted.
The report, from the Office of Rail Regulation (ORR), also showed 74% of the study participants said rail firms do "not very much" or "nothing at all" to proactively provide information about compensation when there are delays.
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Only around 20% of the passengers said this information was readily available and around half said they were not particularly confident they could even find the information if they looked for it.
ORR chairman Anna Walker said: "Our research suggests that simply putting information on a website, or only making it available on request, is not sufficient to help consumers be aware of or exercise their rights.
"Britain's rail industry needs to be more transparent and proactive in providing information."
Michael Roberts, director general of industry body the Rail Delivery Group, said: "Compensation has become increasingly generous and easier to apply for in recent years. But this research makes clear that there is more to be done to ensure passengers know their rights.
"Operators are keen to respond to customer feedback and will continue to work with the ORR and others to raise awareness and confidence."