The party plans to cut 66,000 flights a year from Heathrow by tempting passengers on to the first new rail line north of London in more than a century.

The £20bn rail link would run between London's St Pancras station and Birmingham, Manchester and Leeds.

The Tories say it would cost £1.3bn a year for 12 years. Taxpayers would fund 75% and the private sector 25%.

The line would be completely new and would allow the existing West Coast main line to be used for commuter journeys between smaller towns, such as Macclesfield, Stafford and Milton Keynes, and the big cities. There would also be a high-speed line linking St Pancras with Heathrow.

Estimated journey times on the 180mph line would be cut: London to Manchester would be cut from 125 minutes to 80 minutes, while the trip from Manchester to Leeds would be cut from 55 minutes to 17 minutes. London to Birmingham would take 45 minutes instead of 80 while London to Leeds would be 97 minutes instead of 125.

The Conservatives will announce more detailed plans at their party conference in Birmingham on Tuesday.