The transport secretary is facing calls to set out his plans for the future of Northern rail, after suggesting he could strip the train operator of its franchise.

Speaking on BBC Breakfast on Thursday, Grant Shapps said he had written a “request for proposal” in the autumn, starting a process in which Northern could lose the franchise or be given a short-term contract.

He added: “I’m simply not prepared to have the service on Northern to carry on as it is and I’m taking action.”

Although many train users and transport campaigners welcomed the strong rhetoric, others pointed out that little had changed since Shapps first outlined his plans back in October.

The director of the Northern Powerhouse Partnership, Henri Murison, said the transport secretary’s comments “reflect the position as it has stood for some time now. The key issue is what happens next.”

He argued that TransPennine Express, another rail operator in the north, should also face a franchise review for its poor service, and that more power should be awarded to metro mayors in the region, along with Transport for the North, to create an “integrated London-style network”.

Andy Burnham and Steve Rotheram, the mayors of Greater Manchester and Liverpool respectively, have been campaigning for Arriva-owned Northern to be removed from the franchise, and are worried about Shapps’s lack of clarity.

Burnham said: “I am concerned that he has left on the table the possibility of Northern having a different form of contract. That would be a reward for failure and completely unacceptable to us.”

Rotheram said: “This is not good enough. Passengers and staff need clarity, so the secretary of state should urgently explain his statement and set out a clear plan as to how he will bring back stability to our railways.”

Campaigners have also pointed out that government underfunding of infrastructure is also to blame for problems, such as insufficient capacity at certain stations and on some areas of track, an issue which Shapps failed to address.

Meanwhile, the general secretary of the RMT union, Mick Cash, said Shapps’s comments were “a dead cat being slung on the table to distract from the fare rise scandal”.

“If Grant Shapps was serious he would set out a timetable for removing the Northern rail franchise from Arriva and their replacement with the public sector operator.”