A cross-party fightback against mounting criticism of a planned high-speed rail link gained momentum as advocates switched focus from reduced journey times to the need to ease overcrowding.
Transport Secretary Patrick McLoughln said it had been "wrong" to try to sell it on the basis of speed, conceding cutting 20 minutes off a journey from London to Birmingham was "almost irrelevant".
But he insisted the north-south link - which will also go to Manchester and Leeds - was "essential for the future competitive edge" of the UK.
He was bolstered by a strong defence of the controversial project from his Labour shadow Maria Eagle, who said Britain's creaking rail network was doomed to "failure" without it.
Amid speculation Labour could drop its support, she said there was "no reason" why it could not built on time and on budget, and urged ministers to "crack on" with the necessary legislation.
The pair took to the media to defend the project on the eve of the publication of a report by the Commons public accounts committee which will be highly critical.
The Government's commitment to HS2 was questioned in recent days after the Treasury's top civil servant, Sir Nicholas Macpherson, said there was "no blank cheque" for the project.
Official estimates of the cost were increased by £10 billion to £42.6 billion earlier this year and some observers have argued that even this sum is too low and could rise as high as £80 billion.
It has proved deeply controversial among many communities which will be disrupted by construction work and train noise along the route - many represented by Tory MPs who could rebel on the issue.
Calls for it to be abandoned have also come from Alistair Darling, who as chancellor under the last Labour government approved the deal, and the Institute for Directors. But Prime Minister David Cameron has said he is "passionately in favour" of the flagship project, and denounced an "unholy alliance" of critics who see it as a white elephant.