The consumer group looked at the online claims forms of 24 train companies and found they required between 10 and 24 bits of information from passengers seeking compensation for delayed or cancelled journeys. These included information on whether they held a paper ticket, the cost, class, whether it was peak time, the dates of validity and how it was paid for.

It called on train companies to introduce automatic compensation.

The worst offenders were Greater Anglia, London Northwestern, ScotRail, Transport for Wales and West Midlands. Each rail group demanded 24 pieces of information before issuing a claim. Chiltern Railways and Heathrow Express were the best-performers, but even then, asked for 10 different pieces of information.

Around two-thirds of passengers don’t claim compensation for delays. According to Which?’s annual rail passenger survey, a third of those claims weren’t made because it was too much effort.

Which? showed six of the train companies also asked people to provide the ‘from and to’ journey details more than once on the same form, leaving them inputting journey details twice.

Alex Hayman, Which? managing director of public markets, said: “It’s clear this fragmented and confusing compensation system leads to people losing out on a lot of money when they have already suffered enough from unacceptable levels of delays and cancellation.

“The technology exists to deliver compensation automatically, but the industry continues to drag its heels, while benefiting from a system that deters passengers from claiming the money they are owed.”