Bosses at HS2 today said they are "on track" to begin construction work on the high speed rail line in 2017 after Supreme Court judges rejected a legal challenge to the plan.
The governments Hybrid Bill - which paves the way for the work - can now proceed with a new deadline of February 27.
A HS2 spokesman said:
We saw today the Supreme Court unanimously rejecting technical challenges which had no bearing on the need for a new north south railway. We remain on track to get the scheme ready for construction in 2017.
HS2 is essential in helping rebalance UK growth - bringing greater prosperity to the Midlands and the north and delivering essential additional capacity for more trains and passengers across the network.
Video from the Supreme Court shows the moment judges unanimously rejected an appeal by anti-HS2 campaigners challenging the HS2 project.
Protest group HS2AA challenged the Secretary of State's decision to introduce a bill in Parliament to authorise the development of the high-speed rail link from London to the Midlands and north.
Their objections hinged on claims that MPs would not apply an "independent mind" to the proposals; that the time allowed for debate was too short; and that most members were "unlikely" to attend the debate anyway.
Lord Reid said:
These arguments were rejected by the High Court, and by a majority in the Court of Appeal.
The further appeal to this court is unanimously dismissed.
Action group HS2 Action Alliance (HS2AA) have told ITV News Central they plan to take their protest to the next level after the UK Supreme Court rejected their latest bid to halt the project, vowing: "We will take this to Europe."
A panel at the Supreme Court were told yesterday that more than 50 ancient woodlands sit on the proposed HS2 route of the new high-speed line that proposes to link London with the Midlands and the North.
David Elvin QC, speaking on behalf of anti-HS2 campaigners HS2 Action Alliance, told the Supreme Court justices that at least 10 sites of special scientific exercise, more than 50 ancient woodlands, four Wildlife Trust reserves and numerous local wildlife sites were on the proposed HS2 route.
Calling the case 'the most important strategic rail decision this country has taken for a generation', Mr Elvin also said that 170,000 homes lay within a kilometre of the proposed line.
HS2AA hope to overturn a 2-1 majority Court of Appeal ruling which went against a reassessment of the project.
Campaigners seeking a reassessment of the high-speed rail project in the Supreme Court accused the government of 'cutting corners' at the first day of the high court challenge yesterday.
HS2 Action Alliance (HS2AA), who wish to force a further environmental assessment of the current scheme to link London, the Midlands and the North, are hoping to overturn a decision by the Court of Appeal.
David Elvin QC, appearing for HS2AA, argued that the phases were not reviewed as a whole.
He said: "What we have here is a cutting of corners."
"This is not simply an academic exercise seeking to identify breaches of European law. It is a real defect because the Government intended the consultation exercise to be wide ranging."
The new chairman of HS2 told MPs yesterday that the line is 'not just about speed', ahead of a challenge in the Supreme Court today from HS2 Action Alliance and local councils, who are hoping to force a further assessment of the plans.
Sir David Higgins, who is to take over as chairman of HS2 Ltd, said: "To date, everyone has focused on speed. To me, it [HS2] has never been about speed. It is about capacity - the bottom of the West Coast main line is full.
"It's also about connectivity."
Mr Higgins, who is currently chief executive of Network Rail, told the House of Commons Transport Committee that he had been keen to get involved with HS2 because he feared the complex project was becoming 'a political football'.
The Government's plans to go full steam ahead with the HS2 high-speed rail project are to be challenged today in the Supreme Court.
The highest court in the land will hear the case of the HS2 Action Alliance and local councils to force a further assessment of the scheme, after they lost a bid in the Court of Appeal.
A Department for Transport spokesman said: "The Government will continue to defend any challenge in the Supreme Court, but strongly believes Parliament is the right place to debate the merits of HS2, not the courts."
Anti-HS2 group the HS2 Action Alliance (HS2AA) says the line will have "a hugely damaging" environmental impact up and down the line, threatening 350 unique wildlife habitats, 30 river corridors and 24 sites of Special Scientific Interest.
The group says a thousand people donated £50 each over five days to fund the Supreme Court action.
It's is a sad day when hard working tax-payers have to take the Government to the highest court in the land to ensure that it protects irreplaceable environments for future generations.
The very fact that we have been given the right to appeal to the Supreme Court and seven judges are sitting shows the vital importance of this case, not just for the right decisions to be made around HS2, but for future national infrastructure projects.