An inquiry has been launched into the sale of train tickets after a watchdog warned that passengers may have been "misled" over festive travel.
Transport Secretary Chris Grayling ordered an "immediate investigation" after Transport Focus found passengers could buy tickets for services that will not run due to Network Rail's engineering work.
Analysis by the passenger group revealed more than 2,600 omissions or errors relating to trains or replacement buses on journey planners.
It also found that six rail firms had failed to offer a full range of advance purchase tickets 12 weeks before Christmas when timetables should have been released, meaning some passengers could be forced into buying more expensive tickets.
Mr Grayling said: "It would be totally unacceptable if any passenger has to pay walk-up fares this Christmas because advance tickets were not available.
"I expect passengers to be offered the highest standards of customer service and have ordered an immediate investigation into this report."
The Transport Secretary urged Network Rail and train companies to "work more closely together to minimise disruption for passengers and ensure this issue does not happen again".
Plans were revealed last month to bring the operation of tracks and trains closer together in a bid to boost reliability.
By October 13, 11 weeks before Christmas, reservations for the Christmas week had still not opened on Great Western, London Midland, South Western Railway and Southern, the Transport Focus report found.
Only 15% of services were open for reservation on Greater Anglia and 25% on Virgin Trains.
Transport Focus 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?"
In a letter to Transport Focus, Paul Plummer, chief executive of industry group the Rail Delivery Group, said: "We clearly all agree this is important."
He said all members would "develop a plan and get back to you more fully before Christmas".
The report's findings come following the recent announcement that average ticket prices are set to rise by 3.4% in the new year.
Shadow rail minister Rachael Maskell said: "Not only will passengers suffer the steepest fare hike in five years in January, they are also being tricked into buying tickets for non-existent services over Christmas."