Massive problems with rail services at Huntingdon and St Neots stations are “totally unacceptable” MP Jonathan Djanogly has said.
He welcomed an inquiry into the mess called by Transport Secretary Chris Grayling.
Passengers have been complaining about major disruption to services since a total overhaul of the timetable was introduced a fortnight ago.
Mr Djanogly said: "I have been contacted by a significant number of constituents complaining about the service. It is absolutely unacceptable and the timing of it is such that the operators should have seen what was coming."
He said the train operators and Network Rail had been involved in a "blame game" over who was responsible.
"I am very pleased that the Secretary of State has announced an inquiry and that the Transport Select Committee has also said it will hold an inquiry," Mr Djanogly said.
He said he and North East Bedfordshire MP Alistair Burt met train operator Govia, whose Great Northern trains stop at Huntingdon and St Neots, on Tuesday morning and welcomed the introduction of a "stable and reliable" temporary timetable.
"It will not be the full May timetable and it will mean one or two less peak trains," Mr Djanogly said. "What they are calling a stable and reliable programme will be in place for the next five or six weeks until they can run the full timetable."
Mr Djanogly said passengers should still check travel times the night before and that the trains shown were expected to run, although there may be some delays as GNER trains would be making extra stops.
Anne Hall, who commutes from St Neots, said: "This morning (Monday) back to work to discover that the first train was rumoured to be at 06.03 from St Neots and the one which I caught was at 06.59 to Kings Cross where they had managed to lose four carriages. A good job I managed to get on it.
"There was nothing else showing until around 8.30.
"I dread trying to get home this evening. It is much worse than the first week. If it is so unworkable why can't they go back to the old timetable until they get it sorted out. It is appalling, commuters are extremely angry."
Shift worker Frank Hope accused GTR of having a "gung-ho" attitude towards bringing in the new timetable and that the situation should be addressed.
Mr Hope, a Transport for London worker, said: "When you have done an eight hour shift you don't want to be waiting an hour and a half to get a train home."
Govia Thameslink spokesperson said: "May's new timetable was part of the biggest change to services for decades, introducing 400 extra services and providing longer trains to address the doubling of passengers on our network in just 16 years.
"We always said it would be challenging and we apologise sincerely for the significant disruption being experienced by passengers. Delayed approval of the timetable led to an unexpected need to substantially adjust our plans and resources in an unexpectedly short time-frame.
"We are working with industry colleagues to introduce changes that will progressively deliver improvement. In the meantime, we have removed around 230 trains from the Thameslink and Great Northern timetables this week so there are fewer unplanned cancellations, allowing passengers to arrange their journeys with greater confidence."