The government has given the go-ahead for all proposed sections of the HS2 high speed rail scheme across England, despite spiralling costs and local environmental concerns over the controversial project, Boris Johnson announced today.

The Prime Minister told MPs in Parliament today his government was backing plans to construct both phases of the major electric rail scheme, including the initial London to Birmingham route, as well as the later scheduled section running between Birmingham and Leeds and Manchester.

"We have a choice - we can try to get by… or we can have the guts to take a decision, no matter how difficult and how controversial, that will deliver prosperity to every part of the country," he told MPs. "The government has given high speed rail the green signal. We are going to get this done."

The first phase could be up and running by the end of the decade, he said while the second is currently scheduled to open between 2035-40, with the Department for Transport previously estimating the project could triple the capacity of trains running across the entire route.

The project has encounter fierce opposition in local communities affected across the planned HS2 route, while environmental groups and the Green Party have argued the project would destroy ancient woodland and important habitats at a huge cost to the taxpayer. At the same time the government has come under significant pressure to approve the scheme from metropolitan mayors and councils in the north and midlands keen for greater rail connectivity outside London.

An independent HS2 review published by the government today said there was a risk of the project running up costs as high as £100bn, almost double the £56bn budget forecast back in 2015, while also conceding that construction of the new rail network could push up carbon emissions.

Nevertheless, the Oakervee Review recommended giving the go-ahead for controversial project, concluding it could benefit the economy and play a part in achieving the UK's statutory 2050 net zero emissions target by encouraging more passengers away from road and air travel.

And today Johnson said Review left "no doubt of the clinching case for high speed rail", arguing HS2 would boost connectivity and the economy, particularly in areas of the north, as well as speeding up journey times between key regions of England.

He also said the government would also integrate phase two of HS2 with the Northern Powerhouse Rail project to deliver a train route running between Leeds and Manchester, but conceded the costs of the project had "exploded" and promised to appoint a new government minister to oversee HS2.

"I cannot say that HS2 Ltd [the developer behind the project] has distinguished itself in the handling of local communities," the Prime Minister said. "As everybody knows the cost overcasts have exploded. But poor management to date has not detracted in my view from the fundamental value of the project."

Business body the Confederation of British Industry (CBI) welcomed the decision, pointing to the benefits for added rail capacity and connections to lift regional economic growth, as well as welcoming the government's earlier announcement to deliver £5bn funding for bus and cycling.

But CBI's deputy director general Joshua Hardie also warned the government no to "lose sight" of the need to mitigate environmental impacts of the project.

Excellent to be moving forward. Vital for tackling regional inequalities. But can't lose sight of the need for total determination on helping the communities and environments impacted. Use momentum from COP 26 to turbo charge mitigation https://t.co/Ttv4OxbhFB

— Joshua Hardie (@josh_hardie) February 11, 2020

The Oakervee Review today concluded HS2 would likely add to UK carbon emissions "in the long run" due to the expected emissions generated during its construction, but also said the project had the potential to reduce journeys taken on more carbon intensive forms of transport such as rail and road travel.

It pointed to analysis suggesting HS2 could cut domestic UK flight travel by as much as 11 per cent, largely from fewer flights travelling between London and Edinburgh, and cited rising public concern over climate change which it said could further encourage people towards rail rather than flights.

But it emphasised that HS2 should form part of a wider "integrated government strategy" to decarbonise the entire UK rail network in order to reach net zero, and to encourage behaviour change for more people to opt for public transport over private car use and domestic flight.

"On balance, taking into account both the construction and operation of HS2, it appears that HS2 is likely to be close to carbon neutral, though it is not clear whether overall HS2 is positive or negative for greenhouse gas emissions," the Review states.

Greenpeace UK executive director John Sauven said he was fully in favour of transport that cuts pollution and carbon emissions "but bulldozing through irreplaceable wildlife and nature sites is not the way to go about it".

He claimed over 100 ancient woodlands would be damaged or destroyed, along with 33 sites of special scientific interest and "hundreds" of local wildlife sites.

"Giving the go-ahead to such a costly and damaging project is a missed opportunity," he said. "The Prime Minister should have created a first-class regional rail and bus service, up and running across the north in years rather than decades and without adding to the climate and nature emergency."

Nikki Williams, director of campaigns and policy at The Wildlife Trusts, called for a redesign of the project. "Green and sustainable transport is vital, but the climate emergency will not be solved by making the nature crisis worse," she said.