An emergency timetable has been introduced on South Western Railway diesel services west of Basingstoke, after drivers reported that the speed of their trains was reduced.

The problem, affecting trains from Salisbury and Exeter depots, has been identified as being caused by their fuel, although no further details have been released.

Drivers began to report the problem on Wednesday, and the link with fuel was discovered within 24 hours. The affected trains have been taken out of service, and timetables have been cut. An investigation is under way.

South Western said there would be an hourly service between Basingstoke and Salisbury and a train every two hours between Salisbury and Southampton via Romsey, and also between Salisbury and Exeter St Davids. Trains from London Waterloo to Exeter St David’s will be terminated at Salisbury.

SWR chief operating officer Stuart Meek said: ‘We’re very sorry for the disruption that will be felt by our customers on the West of England Line, in the Romsey area and other destinations west of Salisbury. Over the last two days some services have suffered delays due to a fuel problem and so we have had no choice but to withdraw the affected trains.

‘With fewer trains available and a risk of delays, which would have a knock-on effect on the wider network, we have had to make the difficult decision to operate an amended timetable. While we appreciate it is frustrating that fewer services will be operating, this timetable does give our customers a service they can have confidence in.’