Some disabled passengers are still being left stranded on trains or waiting on the platform without help, despite booking assistance from rail companies, according to Passenger Focus.
The customer watchdog monitored nearly 200 "mystery shopper" journeys taken by passengers with mobility impairments, wheelchair users and those with visual disabilities.
One passenger was "left alone at the edge of the platform by the yellow line" and felt "very vulnerable and frightened as a train passed very close by".
Another traveller found the service by staff "poor and bordering on the comical" while another encountered rude staff.
However, some disabled passengers found the service "outstanding and excellent".
Overall, 70 per cent of the mystery shoppers said they were
satisfied with the service they received having booked through the assisted passenger reservation system.
Passenger Focus chief executive Anthony Smith said: "There were too many instances of staff not being adequately trained, people being left stranded without help and, in some cases, not being treated in a decent or dignified way.
"These problems must be sorted out for today's passengers and those who will be putting the service to the test during the (London) Olympics and Paralympics in 2012."
The Association of Train Operating Companies said: "Where there have been cases of disabled passengers failing to receive the level of service they expect and deserve, clearly that is unacceptable.
"That is why train companies have been working closely with disability groups, Passenger Focus and the rest of the industry to help ensure we continue to focus on improving the service.
"However, the Passenger Focus survey does not properly reflect the real improvements in the service offered to disabled passengers in recent years."