Transport Secretary Patrick McLoughlin has defended the proposed HS2 high-speed rail project as "vitally important" to Britain's economic future, after a scathing parliamentary report found the Government had failed to make a "convincing strategic case" for the £42 billion scheme.
In a withering assessment of the proposed link between London and cities in the Midlands and the North of England, the House of Commons Public Accounts Committee said the apparent benefits were dwindling as the costs spiralled.
Ministers' case for the massive project was based on "fragile numbers, out-of-date data and assumptions which do not reflect real life" with no evidence that it would aid regional economies rather than sucking even more activity into London, said the report.
It also warned that an "unrealistic" target of securing the necessary legislation by 2015 risked a repeat of costly errors such as the botched West Coast main line franchise award but Mr McLoughlin insisted that the project can be completed within budget and will benefit the United Kingdom as a whole.
He told the BBC Radio 4 Today programme: "We set a budget. The budget is very clear. It is a £42 billion budget, including a £14 billion contingency. The Mayor of London says it'll be 70, someone else says it'll be 80, soon we'll have someone saying it's £100 billion. The simple fact is we've got to deliver it within that budget.
"I believe it is for the benefit of the long-term future of the United Kingdom. If we are going to be able to compete globally, we need to be able to attract businesses to our cities. To attract businesses to our cities, there need to be good connections. That is vitally important to the future of this country long term."
The report said there is insufficient evidence that HS2 is "the most effective and economic way of responding to future demand patterns, that the figures predicting future demand are robust and credible and that the improved connectivity between London and regional cities will enhance growth and activity in the regions rather than sucking more activity into London".
Committee chair Margaret Hodge questioned whether building the planned line, initially running from London to Birmingham by 2026 before being extended to Manchester and Leeds in 2033, was the best use of money available to upgrade Britain's railways.
She told the BBC: "The question my committee would ask is if you've got £50 billion to spend on the railways, should you be spending it here? Wouldn't it be better to ease the commuter congestion on this line by looking at longer trains, longer platforms, more frequent trains? Wouldn't it be more sensible to try, if you want to really stimulate activity in the regional cities, to do things like linking Bristol right across to Liverpool, so that brings them new markets?"
The Government's commitment to HS2 has been questioned in recent days but David Cameron has declared himself "passionately in favour" of it, and the Government is shortly to launch campaign to bolster support. Stop HS2 chair Penny Gaines said: "We are told the Prime Minister has personally ordered a fightback on HS2. We hope he actually takes note of what this report says and cancels HS2."