New high-speed railway lines linking Oxford with London in about 30 minutes could be on the way, after Network Rail said it was looking at ways to increase capacity to meet rising demand for rail services.

A feasibility study into lines suitable for trains like the French TGV and Eurostar will include the two routes between the capital and Oxfordshire.

The rail infrastructure company is to study five key routes running north and west of London, including the Great Western Main Line to Didcot, Oxford and the West of England, and the Chiltern Line, linking London with the West Midlands via Haddenham & Thame, Bicester and Banbury.

The review will also look at the East Coast, West Coast and Midland Main Line routes as Network Rail explores ways to cope with projected future growth after a 40 per cent rise in passenger numbers in the past decade.

Any new routes would probably run alongside or close to existing rail routes or motorways, to minimise the environmental impact.

Last November, the final section of the High Speed One line, between London St Pancras and Ebbsfleet, in Kent, was opened, allowing Eurostar trains to France and Belgium to run at up to 186mph (300kmh) all the way to the Channel Tunnel.

From next year, commuter trains serving Kent will start to use the route. Class 395 trains, built by Japanese firm Hitachi, will run at 140mph, slashing the journey time between Ashford and London from 83 minutes to just 36 minutes.

A Network Rail spokesman said: "Dedicated new lines would help free up a lot of capacity on the existing network, providing space for a lot more services.

"Potentially, high-speed lines are a solution we are looking at, but they would be a political decision, with a large capital cost attached."