The Office of Rail and Road (ORR) will publish a report on Thursday into what went wrong with the new timetable, which was introduced in May.
Passengers on Northern and Thameslink networks were particularly badly hit, leaving tens of thousands stranded by reduced or cancelled services.
The report is expected to be hard hitting, and critical of the train operators, Network Rail and the Department for Transport (DfT).
Sources said the report will conclude there is no leadership in the rail industry, leading to speculation that a new authority may be established.
The Strategic Rail Authority, a non-departmental public body set up to provide strategic direction for the railway industry, was abolished in 2006, with its functions absorbed by the Department of Transport or the ORR.
Trade unions representing railway workers are not expected to be criticised in the ORR report.
They had warned that train drivers had not been given enough time to prepare for the new timetable.
The ORR, was asked by Transport Secretary Chris Grayling to set up an inquiry into the May timetable chaos. It was led by its chairman, Stephen Glaister.
Final recommendations to the rail industry and the Government about how to handle major changes in future will be released by the end of the year.
More than a third (36%) of Thameslink trains were delayed by at least five minutes between May 27 and June 23, compared with 18% in the same period last year.
The proportion of Great Northern trains failing to hit the same punctuality target rose from 16% to 30%.
A series of failures have previously been blamed for the timetable chaos, including Network Rail’s delayed electrification projects in the North, poor planning by train operators and the decision by transport ministers to phase in the introduction of new Govia Thameslink Railway services.
Mick Whelan, general secretary of Aslef, the train drivers’ union, said: “The ORR report puts the blame where it belongs, at the door of the train operating companies; the DfT and Network Rail.
“The train companies did not plan properly. They do not employ enough drivers to run the services they promise, in their franchise applications, to deliver and they started driver training far too late. The DfT was, as usual, asleep at the wheel and Network Rail was behind on track enhancements.
“The result was that passengers suffered cancellations, delays and frustration for months. Which would have been far, far worse had it not been for train drivers, and other staff, who showed enormous flexibility in helping the companies through a crisis of their own devising.
“Drivers - who went to work not knowing when or even if they would be able to get home - went above and beyond in helping the train companies provide a service. If it hadn’t been for our help, the disruption would have been far worse than it was.
“The call for proper leadership - a clear indictment of Chris Grayling’s failure to deliver at the DfT - lends weight to suggestions that Theresa May’s railway review, which will also be announced tomorrow, will end up recommending a new version of the Strategic Rail Authority.”