Transport Secretary Chris Grayling has apologised for major disruption following the introduction of new train timetables, while also criticising “failings” by Network Rail.
Hundreds of services have been cancelled by Northern and Govia Thameslink Railway (GTR) since departure times were rescheduled on Sunday.
Mr Grayling said it was “not good enough” for people to face this number of delays and cancellations, adding in the Commons: “I’m sorry this was the case.”
He said the Department for Transport (DfT) and others were working hard to sort the problem, but insisted it was a “major teething problem” in what would be a “step forward for the railways”.
He said he had informed Network Rail bosses that this could not happen again.
Delays to Network Rail infrastructure projects, including electrification work between Manchester and Preston, have contributed to the majority of train journeys in Britain only being confirmed six weeks beforehand rather than the usual 12.
Northern has submitted “urgent plans” to tackle its poor performance, the DfT said.
This would include improving driver rostering, increasing driver training on new routes and putting extra peak services into the timetable on key routes.
DfT officials were “working urgently” with Northern and transport body Transport for the North to improve services.
Mr Grayling will speak to Northern bosses on Thursday to “discuss next steps”.
He said: “We are delivering the most comprehensive and significant modernisation of the national rail network since the Victorian era.
“Introducing new services, providing passengers with faster journeys and delivering more seats will be part of this essential transformation – but the level of disruption that passengers have experienced in the North is unacceptable.
“Improving the service for Northern customers is the number one performance priority for my department and we will work with the industry to keep disruption at a minimum.”
Mr Grayling has come under pressure to take action over the performance of Northern and GTR.
Labour mayor of Greater Manchester Andy Burnham earlier claimed passengers in the north of England were “invisible” to Mr Grayling as he was still waiting for a response to his request on Monday for an “urgent meeting”.
The DfT said rail minister Jo Johnson had spoken to Mr Burnham.
Steve Rotheram, mayor of Liverpool City Region, claimed there was a “lack of care and consideration for the travelling public”.
A spokesman for Northern accepted it had been a “difficult few days” and apologised for the delays and cancellations.
He added that the timetable shake-up was “the biggest change to local rail for many years” and remained a “significant operational challenge”.
GTR – which consists of Southern, Thameslink, Great Northern and Gatwick Express – had also seen major disruption after the timetable relaunch.
“They must be breaching their contract,” he told the Press Association.
“We want the Secretary of State to look at ending the franchise now rather than in 2021.”
Sir Oliver Heald, Tory MP for North East Hertfordshire, has written to Mr Grayling “asking for a full explanation of how this has occurred”.
He said: “There was no advance notice that there was going to be this scale of disruption. For my constituents it really came out of the blue.”
A GTR spokesman said new services were being added “incrementally” due to the “scale and complexity of the task” which involves redeploying drivers and trains as well as changing operating practices.
He insisted passengers would benefit from an “overall increase in capacity with immediate effect”.
The rail timetable is updated twice a year, but the latest update has seven times more changes than normal due to the introduction of new trains and a bid to make existing services more reliable.
A Network Rail spokeswoman said: “Late timetables have certainly not helped the recent events, but there are many other factors involved and we are looking at understanding the root cause so that future changes can be implemented more smoothly.”