Oxfordshire rail services are at the top and bottom of the league for punctuality, according to the latest official figures.

Chiltern Railways, which links Banbury and Bicester with London Marylebone and Birmingham, is top of the table, with 95.6 per cent of its trains on time in the last three months of 2007, said the Office of Rail Regulation (ORR).

But bringing up the rear is First Great Western (FGW), which links the county with London Paddington, the West of England and South Wales, which ran just 79.7 per cent of trains on time.

FGW's service was recently branded "unacceptable" by ministers.

The ORR is currently overseeing a joint performance improvement plan - developed by track and signal operator Network Rail and FGW - aimed at improving performance on the route and on Wednesday warned Network Rail that it could face severe consequences if it did not cut the amount of delays on the FGW network that it was responsible for.

A spokesman for FGW said: "FGW has accepted that it has not provided the service levels its customers deserve and we have put in place an improvement plan that has been agreed with the Department for Transport.

"We are already seeing improved performance and this includes our latest Public Performance Measure figures and cancellation rates - we need to do better to deliver consistently across the FGW Network for all our customers, but we are moving in the right direction."

CrossCountry Trains, which serves Oxford and Banbury, ran 86.9 per cent of services on time during the survey period, exactly matching the overall on time performance of the country's passenger train operators.

The franchise was taken over by Arriva from Virgin last November.