Moves to reinstate double track on some or all of the Cotswold Line through west Oxfordshire are running late.

The route has one of the poorest punctuality records on the entire rail network, with barely 70 per cent of its trains running on time. The industry average is 90.8 per cent of trains on time.

The first few days of the new timetable this week have shown little sign of improvement, with delays to morning peak trains.

Network Rail announced in February that it was spending £150,000 to investigate ways to end delays caused by the long single-track sections on the line, including one of 14 miles from North Oxford to Ascott- under-Wychwood.

The company said at the time that it expected to reveal a list of options for enhancement work by the autumn.

But an announcement will not now be made until early next year. Spokesman Michael Cavanagh said: "Network Rail remains committed to developing a feasible option to improve performance and capacity on the Cotswold Line.

"This is a detailed piece of work and we expect to be in a position to publish the results of the feasibility study in February."

Adrian Saunders, Oxfordshire County Council's rail development officer, said the delay was due to a decision to combine some of the study work with an investigation of capacity enhancement ideas for the main line through Oxford.

It is not yet known if the delay will affect the timetable for upgrade work on the Cotswold Line, which was projected for completion by December 2010.

Network Rail is understood to be considering whether to reinstate double track on the entire 50-mile route between Oxford and Worcester, or to redouble one or more of the three single-track sections.

The line was double track throughout until 1971, when British Rail removed one set of rails from all but the 11 miles between Moreton-in-Marsh, Kingham and Ascott-under-Wychwood to cut costs.

The only other place on the route where trains can pass each other is Evesham station, in Worcestershire.

Growing numbers of trains using the line in the past 15 years have made timetabling services through the single-track sections increasingly difficult. One late-running train can cause knock-on delays to other services for several hours.

* An online petition calling on Prime Minister Gordon Brown to order reinstatement of double track has been set up at http://petitions.pm.gov.uk/Cotswold/