LONDON — British Prime Minister Boris Johnson on Tuesday gave his backing for the new HS2 high-speed railway, despite concerns about soaring costs and opposition from his own MPs.

Johnson said the project linking London to central and northern England was crucial to his plan to rebalance the British economy away from the dominance of London and the southeast, while also tackling climate change.

"If we start now, services could be running by the end of the decade. So today ... the cabinet has given high speed rail the green signal," he told the House of Commons.

Echoing his promise in December's election to "Get Brexit Done", which saw Britain leave the European Union on January 31, he added: "We are going to get this done."

First mooted by the government in 2009, HS2 is the largest current infrastructure project in Europe.

Preparations for the first stage of the line from London to Birmingham are already well advanced, while a second phase is planned to Manchester and Leeds further north.

But critics have called for it to be scrapped, after years of delays and projections of a cost of more than £100 billion ($129 billion, 118 billion euros).

Many MPs, including in Johnson's Conservative party, have said the money could be better spent.

There are also concerns about the impact on wildlife and the environment, as the line goes through numerous sections of ancient woodland.

However, Johnson is known for his enthusiasm for infrastructure, and has promised to rebalance Britain's London-centric economy by investing in the north.

"Poor management to date has not detracted, in my view, from the fundamental value of the project," he told MPs.

However, he announced changes to the way the project will be managed, including a new full-time ministerial post overseeing the railway.

Johnson said HS2 was part of "a revolution in this nation's public transport provision", which also includes new funds for local bus and cycling networks.

"In the 21st century this United Kingdom still has the vision to dream big dreams and the courage to bring those dreams about," he said.

Johnson announced a review of the project last year, and said Tuesday it had confirmed the "clinching case for high-speed rail".

HS2 claims that its trains will connect around 30 million people when it is complete — almost half the UK population — delivering faster journeys and taking pressure off existing rail networks.

It also says that the project will tackle climate change, by taking cars off the roads.

The main opposition Labour party said the scheme should go ahead, but transport spokesman Andy McDonald said the government must "get a grip with the spiralling costs".

The British Chambers of Commerce also welcomed the news, but said it was important that the whole line be built to ensure benefits across the north of England.

"It's time to stop debating and start delivering the new capacity and connections that HS2 will bring to our communities and businesses," said director general Adam Marshall.

But the right-wing Institute of Economic Affairs said it was "deeply disappointing".

"The costs are now likely to exceed the benefits," said the think tank's head of transport, Richard Wellings.

The previous government last year noted that HS2 costs had soared owing to the complexity of building in densely populated cities and challenging ground conditions.

The line runs through some high-end real-estate, as well as archaeological sites, including a burial ground for 40,000 bodies underneath London's Euston Station.

At the same time, it was revealed that rather than opening in 2026, the first phase of HS2 would not operate until sometime between 2028 and 2031.

Preparatory costs are said to have already hit eight billion pounds.

HS2 would be Britain's second high-speed rail project after HS1, the line linking London with the Channel Tunnel to France.

Governments around the world are under pressure to promote cleaner travel as they try to limit climate change by cutting carbon emissions.

As part of a wider plan to promote greener transport, the German government last month agreed to pump 62 billion euros ($68 billion, £53 billion) into its rail network. — AFP