Conservatives have welcomed the Government's "change of heart" on high-speed rail but warned its plans were "flawed".

Shadow transport secretary Theresa Villiers said the Conservatives were not prepared to "blindly accept" the route proposed by ministers.

And she insisted that her party, if elected to power at the election, would start work on the project in 2015 - two years earlier than the Government's plan.

Ms Villiers also warned that when it came to Heathrow, "Labour still don't get" - because ministers had failed to integrate the airport into the high-speed rail (HSR) network.

"In leaving Heathrow out and setting out plans that don't give costed, timetabled and watertight guarantees to take the line north of the Midlands, Labour's plans are flawed by a lack of credibility."

Her comments came after Transport Secretary Lord Adonis announced to peers that work on the first stage of a national network would not begin until 2017, linking London and Birmingham with a line capable of carrying trains reaching 250mph.

Future plans would create a y-shaped, 335-mile network stretching north from Birmingham to population centres either side of the Pennines and in Scotland.

After repeating the statement in the Commons, Transport minister Sadiq Khan said he was "shocked" by the Opposition's response and claimed it showed the Conservatives were "unfit" to govern.

Ms Villiers said it was vital to catch up on a "high speed revolution" most of Europe embarked on "more than a generation ago".

She said her party had "totally transformed" the debate on HSR with its promise to build a North-South line, as a first step towards the creation of a national network.

"We welcome Labour's change of heart on HSR. But we regret the remit they gave HS2 lacked ambition, that it focused only on the West Midlands as stage one - whereas we want to go further and faster, with our guaranteed, costed and timetabled commitment to take HSR to Birmingham, Manchester and Leeds ..."

She warned: "If we are to get the full environmental benefits of HSR, it's crucial we make it as easy as possible for people to switch from the plane to the train."

The closest HS2's proposals would get to Heathrow was about 10 miles away at Old Oak Common.

"The idea that some kind of Wormwood Scrubs International station is the best rail solution for Heathrow is just not credible."

Mr Khan responded: "I find that incredible. I'm just shocked by your response. If ever evidence was required as to why this lot are unfit to form a government, you've answered the question."

He accused the Tories of "back of an envelope" calculations and asked how meaningful consultation could be undertaken with a construction start date of 2015.

Of her charge on leaving out Heathrow, he said most people wanted to go to London and did not want to be "delayed by going to Heathrow".

Liberal Democrat spokesman Norman Baker welcomed the development, saying his party had been calling for it for years.

Mr Baker said: "Britain has trailed behind Europe for a long time on HSR and I very much welcome the fact that something we have been calling for for years has finally been brought forward by this Government."

Mr Baker sought guarantees that money would not be "raided" from existing rail projects to pay for HSR and asked for a long-term commitment to extend it to Scotland.

He also hit out at the Tories, saying: "This is a matter of national importance which requires consensus in the House and all parties ought to approach it in that matter.

"Do you therefore share my concern that this is an attempt by the Conservative side to create some sort of synthetic, candy-floss row at this point rather than trying to move forward in a sensible, constructive way.

"They appear to be putting short-term politics before the long-term interests of the country."

Mr Khan said he was "disappointed" the cross-party consensus had broken down and accused the Tories of trying to create "dividing lines that should not be there".

Evidence suggested HSR would regenerate parts of the country, he said, and would result in 8-11% of domestic air passengers switching to the railways.

Louise Ellman, Labour chairman of the Commons transport select committee, said she was "delighted" that her group's vision for HSR was being translated in to reality.

But she asked when the economic regeneration would take place.

Mr Khan said investors would start putting money in immediately now that plans for HSR were in place.

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