"I am horrified that the level of passenger dissatisfaction should have grown to such an extent and so rapidly," said CRUCC national director Paul Hadley.
Information at stations and from national telephone inquiry bureaux topped the list of complaints, followed by reliability, overcrowding, on-train cleanliness, suitability of service and punctuality.
Train companies have fared badly - in part due to problems with the ailing rail infrastructure. In London, complaints reached an all-time high, with Connex South Central seeing the number of letters it receives rise by 158 per cent.
The West of England also suffered. The passenger watchdog received 1,240 letters in the first 6 months of the year, compared with 1,397 in the preceding 12 months. Mr Hadley said the figures "must set the alarm bells ringing. It is evidence of just how wide the gulf is becoming between passengers' expectations and operators' performance."Reuse content