Train operator Govia Thameslink had assured the secretary of state for transport that it was ready to introduce a new timetable three weeks before chaos hit local railway services, Huntingdon MP Jonathan Djanogly has said.
He vowed to hold Govia and transport ministers to account until the mess was put right.
The MP said he had been assured by new Govia boss Patrick Verwer that the situation was improving.
Mr Djanogly and South East Cambridgeshire MP Lucy Frazer met Mr Verwer to discuss massive rail problems which developed after the introduction of a new timetable in May.
Passengers at Huntingdon and St Neots, which are served by Govia's trains, have complained about delays and cancellations since the timetable was first introduced.
A special compensation scheme for season ticket holders has been introduced by Govia.
Mr Djanogly said: "I was assured by Mr Verwer that the new interim timetable which was put in place on July 15 is working and that the situation is now improving with fewer trains being cancelled.
"However, if any of my constituents have found this not to be the case I would like to hear from them via email at email@example.com so I can raise their concerns with Govia."
Mr Djanogly said: "Following representations from constituents I raised the point that non-season ticket holders are not covered by the new compensation scheme.
"Mr Verwer responded that non-season ticket holders will also be able to apply for compensation through the usual routes if a train is more than 15 minutes late. Govia will be publishing further information on how to claim compensation."
Mr Djanogly said: "As rail service timetables stabilise, it is expected that the full planned May timetable will be introduced in stages over the coming months.
"I understand early analysis has shown that the industry timetable developed by Network Rail was very late to be finalised. This resulted in Govia not having enough time to plan crew schedules or complete crew training.
"But it also emerging that Govia did not have enough drivers with the sufficient route knowledge required to operate the new timetable. It is concerning that Govia assured the transport secretary three weeks before the timetable change that they were ready to implement the changes."
Mr Djanogly added: "I now await the inquiry and please be assured that I will continue to hold both Govia and transport ministers to account until these issues are resolved."
Govia reported a positive start to the introduction of the new interim Thameslink and Great Northern timetable this week.
It said the new schedules had delivered a more stable, resilient and reliable service.
Some 200 extra trains are now running each weekday across the network compared to the period prior to the introduction of the May timetable.
Levels of punctuality and reliability are returning to levels achieved before the May timetable change.