Fast rail would cost £30 billion from 2017

The 535 km route, which would link London to Birmingham, Manchester, Sheffield and Leeds and open in phases from 2026, will not be fully confirmed until public consultation and other preparatory work has been completed, Adonis said on Thursday.

Faster links to Scotland and other northern English cities would be possible by allowing high-speed trains to run on existing tracks running further north, he said.

The government will investigate whether to add an extension to Europe's busiest airport, Heathrow, as desired by the Conservatives and Heathrow's operator, BAA which is majority owned by Spanish Grupo Ferrovial.

"Over the next 20 to 30 years, the UK will require a step-change in transport capacity and connectivity both to promote and respond to long-term economic growth," Adonis told parliament. "High speed rail would be by far the most effective way to achieve this step-change."

Journey times from London to Birmingham would be cut to about 50 minutes from 1-1/2 hours.

Leeds, Sheffield and Manchester would be brought within 80 minutes of the capital, according to Department of Transport figures. Journeys to those cities from London currently take more than two hours.

The first stage of the route, linking a rebuilt London Euston station and a new station in Birmingham, was expected to go to public consultation later this year, Adonis said.

Planning for links to Sheffield, Manchester and Leeds will be finished by mid-2011 and be presented to the public in 2012.

The Conservatives, who could end 13 years of Labour rule at an election expected on May 6, have pledged to extend the route to Heathrow, guarantee links to northern cities beyond Birmingham and start construction in 2015.

"In leaving out Heathrow and setting out plans that give no firm guarantees north of the midlands (Birmingham), Labour's plans are flawed ... by lack of ambition," Conservative transport spokeswoman Theresa Villiers said.

(Editing by Dan Lalor)