Former Defence Secretary Sir Michael Fallon told the Transport Secretary to "get a grip" on the chaos facing train passengers on Northern and Govia Thameslink railways.
In a rare "blue on blue" intervention, the Tory MP for Sevenoaks said there was "real, raw anger" among commuters in his Kent constituency, and criticised Mr Grayling's attempts to pin most of the blame on Network Rail.
As cancellations and delays continued despite the introduction of new temporary timetables designed to halt the disruption, Sir Michael told BBC News: "(Commuters') message to Chris Grayling is this has to be sorted out, and it's no use people blaming each other and talking about one operator being responsible for this and the other that.
"The Secretary of State is in charge and they are very clear that Government in the end has to intervene now and sort this out."
Northern launched an eight-week interim timetable on Monday, removing 165 trains - 6 per cent of services.
Areas affected include Manchester, Liverpool, Blackpool and the Lakes Line between Oxenholme and Windermere.
Govia Thameslink Railway (GTR) - which consists of Southern, Thameslink, Great Northern and Gatwick Express - is also running a temporary timetable enabling passengers to "arrange their journeys with greater confidence".
Some 230 daily services have been removed by GTR, which makes up 6 per cent of scheduled trains.
Northern's policy is for passengers to only claim compensation based on the alternative timetable rather than previous versions.
The reduced timetables failed to stop Monday becoming the start of a third week of rail chaos with the number of trains either cancelled or more than 30 minutes late for Northern and GTR reaching 69 (7 per cent) and 102 (8 per cent) respectively by 12.30pm, according to the trains.im website.
Sir Michael, who quit the Government last year amid allegations of inappropriate conduct, said: "This is now week three and this is becoming a scandal. My constituents can’t get to work in London. Their children can’t get trains to school. And we are now into more cancellations even with the emergency timetable. So it really is time now that ministers got a grip of this and forced Thameslink to get on and run a decent service, if necessary borrowing drivers from other companies who know the routes."
He added: "The Secretary of State is in charge and he’s got to find some solutions to this."
Sir Michael also suggested that Mr Grayling could have done more to oversee public infrastructure operator Network Rail's process of finalising the timetables, and suggested Thameslink may need to be stripped of its franchise, although a spokesman later made clear the MP was against renationalisation.
Asked whether the Transport Secretary's job was in question, Sir Michael said: "There are a lot of questions now as to how this ever happened in the first place, why it wasn’t properly prepared.
"I shall be pressing (Mr Grayling) on how much longer the Thameslink franchise has to run, and whether it is feasible to take the franchise away, or whether that would just simply make the situation even worse. But clearly the Transport Secretary has to demonstrate today that he has this situation on board and that he’s ready to use all his powers to start putting things right. Commuter patience is running very, very thin. There is real anger in the villages."