The Office of Rail and Road says that passengers were let down by the rail industry in a report commissioned after the rail disruption over the summer.
The rail network was plagued by cancellations and delays after new timetables were introduced in May.
Hearing evidence over three months, the inquiry found that Network Rail, Govia Thameslink Railway, Northern, the Department for Transport, and the Office of Rail and Road all made mistakes which contributed to the collapse of services.
It also found that the problem was made worse by a lack of information from train operators when the disruption happened.
One of the key issues the Inquiry found is that there is an apparent gap in industry responsibility and accountability for managing systemic risks.
It also found that:
- The System Operator (SO) function within Network Rail was in the best position to understand and manage the risks, but did not take sufficient action, especially in the critical period of autumn 2017
- Neither GTR nor Northern were properly aware of or prepared for the problems in delivering the timetable and they did not do enough to provide accurate information to passengers when disruption occurred
- Both DfT and ORR are responsible for overseeing aspects of the industry, but neither sufficiently questioned assurances they received from the industry about the risk of disruption.
In response to the report, Northern said it is "deeply sorry for the unacceptable disruption" passengers had faced, saying it apologises unreservedly.
The franchise said they put an emergency timetable in place to try to stabilise services, but that most trains have now been restored. They are giving compensation to customers holding season tickets.
In a statement the company said "Northern will now consider in detail the findings in the ORR Report. We want to learn the lessons of the May timetable disruption and will be working closely with other organisations across the rail industry to ensure new timetabling is implemented as effectively as possible for customers in the future."