Transport Focus has found that travellers are also being offered fares for journeys that will be disrupted by engineering works - and, in some cases, are being denied the chance to buy cheap tickets.
During Christmas week alone, 2,648 incorrect journeys have been listed on databases, meaning customers run the risk of being disappointed on the day they are due to travel.
The passenger watchdog also claims that six rail operators failed to offer a full range of advance purchase tickets 12 weeks before Christmas, which is when timetables should have been released.
By 13 October - 11 weeks before Christmas - reservations had still not opened for Great Western, London Midland, South Western Railway and Southern services.
Just 15% of services were open for reservation on Greater Anglia, and 25% on Virgin Trains.
Transport Focus has called for a review to ensure Network Rail and train operators always publish correct timetables three months in advance.
The watchdog is also demanding that passengers who have already bought tickets are told about changes to services - and any incorrect information on ticket websites is removed promptly.
It said: "Being forced to change plans can be very frustrating and breeds a sense of distrust in the railway. It also raises consumer rights issues: were passengers misled into buying something they would not otherwise have purchased; did they pay more than they needed to?"
Chief executive Anthony Smith added: "Train operators' advice is to book early at Christmas to get the best deal, but if the timetable has not been finalised only more expensive 'on the day' tickets can be bought."
In a letter to Mr Smith, Paul Plummer, chief executive of industry umbrella body Rail Delivery Group - which comprises all passenger and freight rail companies - said: "We clearly all agree this is important."
He added that all members would "develop a plan and get back to you more fully before Christmas".
The findings come just over a week after the industry announced the average cost of a train ticket will rise by 3.4% in January.