Transport giant Arriva's takeover of rail services in northern England has stifled competition and could push up fares on certain routes, the Competition and Markets Authority (CMA) has warned.

Arriva began running the Northern rail franchise in April after it was awarded a nine-year contract by the Department for Transport – but the transport firm already operated a number of rail and bus routes covering the same areas.

The Northern franchise covers rail services in North East and North West England, Yorkshire and the Humber. It covers more stations than any other UK franchise.

The CMA is now investigating Arriva because its "overlapping" rail and bus services leave public transport users in those areas with no choice but to use the firm's services.

In its provisional findings, the CMA has identified four rail routes and nine bus routes where there's now a "substantial lessening of competition" – which could lead to higher fares.

The CMA will now consider what remedies it can take to restore competition to the affected areas. It could decide to curb fare rises on Arriva routes, but has stopped short of threatening to strip the company of its routes.

A final report is due in late October.

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Which routes could be at risk of price hikes?

The following rail routes are said to be at risk of price rises:

  • Leeds to Sheffield
  • Wakefield to Sheffield
  • Chester to Manchester
  • Chester to Stockport

And the following bus routes are also at risk:

  • The 3, X3/X3A and X4 in the Redcar area
  • The 83 and 84 in the Huddersfield area
  • The X14, X15 and X18 in the Ashington area
  • The 12 in the Darlington area

What does Arriva say?

Chris Burchell, managing director of Arriva UK Trains, says: "We have maintained throughout this process that the operation of the Northern franchise by Arriva alongside our existing bus and rail businesses does not create any competition concerns and so we are disappointed that the CMA has identified a small number of these in a handful of local areas.

"This remains an on-going process and Arriva is committed to continuing to engage constructively with the CMA to resolve their concerns and demonstrate that the award of the Northern rail franchise doesn't lessen competition."