A survey by Passenger Focus found that one in 10 people calling GNER and First Great Western were not given the cheapest prices for their journeys. Some were overcharged by more than £200.

The disclosure came as rail companies were accused of bamboozling passengers with a bewildering choice of tickets and prices. A year after the industry promised to make prices more simple, The Daily Telegraph found travellers trying to book tickets on some routes must still choose from up to 40 different fares, each with its own restrictions.

Campaigners yesterday called for the rail industry to "stop dragging its heels" and improve the quality of its information and introduce easier to understand tickets.

Gwyneth Dunwoody, the Labour chairman of the cross-party transport select committee, said: "You can book a cheap flight on a website in a short period of time but if you want to buy a train ticket you need a degree in economics. Information is power and people buying tickets should have ready access to accurate information. They should be told all the alternatives, not just given the one price.

"I know of no other industry where companies make it so complicated to use a service, or so expensive."

Passenger Focus's survey involved 250 calls to five rail companies. Although the companies were "generally good" at quoting the correct price for simple journeys, the call centres struggled with complicated travel plans.

Out of 250 calls, 15 were quoted incorrect prices while 16 were told they could not have a quote. GNER and First Great Western were the worst offenders. Each company gave the wrong information to five out of 50 callers. Virgin quoted the wrong prices for three out of 50 calls.

One caller who asked Virgin for a price for four journeys to different destinations in one week should have been quoted £375 for an All-Line Rover ticket. Instead, Virgin said the trips would cost £638 - an extra £263.

"On the whole, they get the simple fares right but they seem to have problems with the more complicated journeys where there is a choice of routes or fares," said a spokesman for Passenger Focus. "We have been saying for a long time that fares need to be simplified. We need to have meaningful choice."

The train companies insisted that they were improving the quality of their phone and internet information. Virgin Trains said it had set up a new, clearer websites.

First Great Western said its online journey planner had also been revamped, while GNER said the mystery shopping exercise had used "complicated and unusual" journeys, so the results were not representative of its customers' experiences.

"We have simplified the structure of our fares and we have removed some ticket types over the last few years," a spokesman said.

South West Trains was accused this week of making fares more complicated when it introduced a new, higher price for off-peak trains in the morning.

Rail companies also want the Government to de-regulate Saver tickets, a move that could lead to an even greater variety of prices.

A spokesman for the Association of Train Operating Companies said: "We are simplifying the fares."