The transport secretary has voiced “serious concerns” about rail operator CrossCountry and threatened to take action if things do not improve.

In a scathing letter to the train company’s interim directors on Friday, Louise Haigh said she “reluctantly” approved its request to temporarily cut down on services.

CrossCountry has said the timetable reduction is necessary to address a backlog of training required by drivers, something it said had been worsened by recent industrial action.

In a statement, the operator acknowledged its poor service and apologised for the inconvenience of the new timetable, saying it would lead to a more resilient service.

The operator announced the slimmed-down timetable, due to run for three months, from 10 August to 9 November, in July.

In her criticisms of CrossCountry, Ms Haigh said passengers had been “suffering from a substandard service for too long”.

“Over the past year, the level of train cancellations across your company has increased significantly and by your own forecasts, you expected to breach your contractual targets for cancellations in the coming months,” she said.

Ms Haigh said this was unacceptable and that the temporary reduced timetable was not a satisfactory response.

“Put simply, the only reason I accepted your proposal was to give passengers more certainty on which services will run,” Ms Haigh said.

The transport secretary said CrossCountry had been put on a remedial plan to formally ensure the rail operator was working to improving services, while barring the company from profiting off running fewer services.

“If you fail to deliver the Remedial Plan, I will not hesitate to take further action,” Ms Haigh said.

In a statement, CrossCountry acknowledged that service had “fallen below the standards our passengers should expect from us”.

“All too frequently, our passengers have been inconvenienced by on-the-day cancellations, which results in poor quality and reliability of service,” it said.

CrossCountry apologised for the inconvenience the temporary timetable would cause, and said redeployed trains would ensure “97% of our normal daily number of seats” would continue to operate.

“By the end of the temporary timetable, we will have more fully-trained drivers who can work across the network,” the statement said.

The CrossCountry network spans major cities across England and into Scotland.

The operator’s services connect most of the UK’s biggest cities, including Birmingham, Edinburgh, Bristol, Cardiff, Leeds, Sheffield, Nottingham, Newcastle and Manchester.

The Labour government has vowed to renationalise nearly all passenger rail services as existing private contracts expire.

It introduced the Passenger Railway Services (Public Ownership) Bill within its first month in office, before MPs left Parliament for the summer recess.

CrossCountry’s contract, agreed by the previous Conservative government, began in October last year and is due to expire on 12 October 2031.