Passengers will want to see a cap on rail fares on the London to Exeter line to counter a monopoly, a Devon MP has warned.

First Group recently won the South Western rail franchise out of Waterloo, to add to the Great Western route it already runs from Paddington - meaning it will control both lines to Exeter.

The Competition and Markets Authority said it had been investigating the award of the franchise since it was made by the Government in May and was concerned the new monopoly could lead to higher fares or a worse service for passengers.

Ben Bradshaw, the Labour MP for Exeter, said he shared the CMA’s concerns and would be writing to the watchdog as well as raising the issue at the first meeting of the All Party Parliamentary South West rail group.

“Having two separate companies running services on different lines between London and the west country ensures an element of healthy competition,” Mr Bradshaw said.

“If one company gets a monopoly on both routes, there would inevitably be concern that prices could go up and services suffer. Passengers would want to see a price cap imposed or some other mechanism for restricting fares if this goes ahead.”