Engineers found the fault during routine maintenance

It has meant a reduced service with trains running only hourly, on main routes between Birmingham, Manchester and Scotland and between Birmingham and Plymouth and Bournemouth.

However, later on Wednesday a Virgin Trains spokesman said services were expected to return to normal on Thursday, after the safety checks to resolve the problems were being carried out more quickly than first thought.

The entire CrossCountry fleet of Voyager trains was initially pulled from service after problems were spotted during routine maintenance work on Tuesday night.

No CrossCountry trains were running north of Edinburgh and none were stopping at Doncaster, with trains going via Leeds instead.

The Virgin service west of Plymouth was suspended for several hours, but resumed shortly before midday on Wednesday.

Engineers found that a bolt in the transmission system underneath two of the brand new trains had fractured.

'Precautionary' measures

Safety checks were immediately ordered on every one of the 78 Voyagers in the company's new flagship fleet - introduced at a cost of millions of pounds .

The work, which is being carried out in Burton-upon-Trent, Staffordshire, by contractors, Bombardier Transportation, is expected to be completed by Friday.

A Virgin spokesman said: "Both Bombardier and our engineers are looking at it.

"What we have been doing is very much precautionary. If we find a problem, we've got to put safety first."

Unexpected disruption

While checks continue 13 trains in the fleet remain out of service, leading to the temporary timetable.

The Virgin spokesman said: "We anticipate operating at least 70% of our services today and passengers can expect an hourly service on all core routes between Birmingham and Scotland, Manchester, Plymouth and Bournemouth.

"We apologise for the unexpected disruption to our passengers and would like to assure them that their tickets will be valid on all our train services and with all other operators."

He added that passengers who decide to postpone their journeys because of the reduced service can still use their tickets on another day.

Virgin Trains is advising passengers who want more information to contact National Rail Enquiries on 08457 48 49 50 or visit www.nationalrail.co.uk.