The Tories say they would scrap plans for a third runway at Heathrow and switch resources to build a high-speed rail line between London and Leeds.

Shadow transport secretary Theresa Villiers said the Conservative party wanted to cut more than 66,000 flights a year at the London airport.

Instead of building a third runway, they would plan for a new railway line running at speeds of up to 180mph between St Pancras, Birmingham, Manchester and Leeds. There would also be a high-speed line linking St Pancras to Heathrow.

The £20billion new line would encourage travellers to take the train rather than fly.

As well as reducing demand for domestic flights, the aim would be to entice people on to Eurostar, now based at St Pancras, for trips to Paris, Brussels and Amsterdam.

The line would also clear the way for more trains on the existing West Coast main line, Ms Villiers told Nicholas Watt of The Guardian newspaper.

Journey times would be slashed, with London to Birmingham taking 45 minutes instead of the current 80 minutes.

Leeds would be 97 minutes from the capital and Manchester 80 minutes. Leeds to Manchester would take just 17 minutes, instead of today's 55.

Ms Villiers said: "This is a seriously green decision. A few years ago it would have been inconceivable for the leader of the Conservative Party to say 'no' to a third runway and putting the brakes on Heathrow expansion."

The Labour Government is "studying" high-speed rail link but has failed to recognise the need for a much more pro-active rail expansion policy.

It has stuck to its environmentally dangerous policies of encouraging highly polluting air travel, as well as building more roads which it has been told by its own experts will merely encourage more traffic.

A study by the engineering consultants WS Atkins found that a high-speed rail network linking London and Heathrow to the North of England and the Midlands would bring benefits of more than £30billion over a 60-year period. High-Speed Rail Report, WS Atkins 2008 summary report