The government has called on rail operators to “urgently set out a comprehensive plan” to resolve the disruption to services caused by cracks found in some high-speed trains.
Hitachi 800 trains were pulled from lines on Saturday as a “precautionary measure” after the fault was found in some carriages.
Great Western Railway (GWR) and London North Eastern Railway (LNER) advised people not to travel over the weekend and today.
Chris Heaton-Harris, the rail minister, said: “I have directed the rail industry to urgently set out a comprehensive plan to ensure services can safely resume as soon as possible.
“I expect operators to explore all options for replacement services to help people complete their journeys and have asked Hitachi for a safety inspection plan, as well as a longer-term repair strategy.
“Our focus is to ensure trains are returned to service as quickly as possible, once they are fully approved as safe. Only then can we start to rebuild a reliable and punctual timetable for passengers. I also want to thank passengers for their patience during what could be a significant period of prolonged disruption, likely to continue for some time.”
The Department for Transport said that Heaton-Harris had called an urgent meeting with MPs yesterday to keep them updated on progress, with representatives from Hitachi and the train operators also invited.
GWR gave warning that its long-distance services would be cancelled today and that local services would be much busier as a result.
LNER also apologised for the disruption, which is affecting most of its services, adding that weekend tickets could be used on trains that are hoped to be running next week.
The Rail Delivery Group warned that the disruption could last for days. Robert Nisbet, regional director at the body, told the BBC: “With the inspections completed initially by the end of today, we are still expecting some disruption to carry on for a few days.
“It’s impossible for me to say exactly how long that is going to take; we are obviously going through this as quickly as possible but we don’t want to rush it.
“We want to ensure that all of those trains are thoroughly inspected and cleared and put into service when things are ready, but there may well be a knock-on effect for some of those timetables into next week.”
He said that the cracks — measuring millimetres — were on the “lifting points on the underside of the carriages used for maintenance”.
Mr Nisbet said: “It’s fair to say this didn’t pose any particular danger to passengers that were travelling on those trains but if you don’t treat these kind of issues early on then they have the potential to develop.”
Hitachi Rail apologised on Saturday for the disruption after the cracks were spotted during routine checks. It added that by Saturday evening “some trains” had been cleared to run as normal.
A spokesman said: “Safety is our number one priority and, as a precaution, the decision was taken to halt the entry into service of our intercity fleets pending inspection.
“We understand the frustration caused and we would like to apologise for the inconvenience caused to passengers and operators. Having been cleared for service, some trains are now running again across the network.”