Rail passengers could face higher fares and worse service following thedecision to award the South West Trains rail franchise to First Group. That is the warning coming from the competition watchdog.

Concerns have been raised by the Competition and Markets Authority aboutthe London to Exeter route as First Group already operates Great Western Railway, which runs the only other train service between the cities.

The South West Trains franchise is currently operated by Stagecoach but will be taken over by First Group, in partnership with Hong Kong-based company MTR, on August 20.

"This is a crucial rail route to the South West, used by around half a million passengers a year. It's therefore vital that passengers do not suffer as a result of reduced competition."

CMA acting chief executive Andrea Coscelli

The firms involved have five working days to offer proposals to address thecompetition concerns.

If these are deemed insufficient the Competition and Markets Authority can open an in-depth investigation.