Train passengers who made more than 220,000 compensation applications for delayed journeys were forced to wait more than a month for their claims to be resolved, figures show.
One in 20 of the 4.2 million claims dealt with between April 1 last year and January 5 was not processed within 20 working days, Office of Rail and Road (ORR) data revealed.
Alex Hayman, managing director of public markets at consumer group Which?, said: “It is unacceptable that train companies have left people making almost a quarter of a million compensation claims waiting more than a month to get a resolution.”
He claimed this is “piling further hassle and stress on passengers” who have already suffered from severe delays and unreliability.
Mr Hayman added: “It’s little wonder trust in the rail industry is worryingly low.
“The Rail Review must ensure that automatic compensation is introduced across the network so that passengers can have their claims resolved quickly and no longer have to jump through hoops to get the money they are owed.”
Former British Airways chief executive Keith Williams is carrying out a wide-ranging Government-commissioned review of the railways.
Which? said public trust in train travel has fallen to 20%, the lowest since it launched its consumer insight tracker in 2012.