Boris Johnson has given HS2 the go-ahead, despite fears over its cost and impact on the environment.

The Prime Minister told the House of Commons that his Government had the guts to take the decision to deliver prosperity across the country.

To avoid further blow outs in HS2's cost or schedule, a series of measures will be taken to restore discipline to the programme, he said.

This will include appointing a minister whose full time job will be to oversee the project, and changes to the way HS2 is managed.

The announcement follows the completion of a Government-commissioned review by former HS2 Ltd chairman Douglas Oakervee into whether or not the programme should be scrapped.

Mr Johnson said: "The review recently conducted by Douglas Oakervee leaves no doubt of the clinching case for high-speed rail.

"A vast increase in capacity with hundreds of thousands of extra seats making it much easier for travellers to move up and down our long, narrow country.

"And that means faster journey times, not just more capacity."

He added one of the reasons why London was so productive was its effective transport system. He said: "As it has expanded, the transport system has brought hope and jobs to people in London and beyond. My government will take this approach and apply it across the whole country.

"People know this country is being held back by its inadequate infrastructure."

He added that HS2 will not just to go Birmingham, but it will go beyond that, and that none of the improvements to rail in the north of England make sense without HS2.

He said: "Let's get it done" and added the first section could be complete by the end of the decade.

Previously, the high-speed line was due to be open between London and Birmingham by 2026, and to Wigan by 2033, but delays mean the final phase to Wigan will not now be complete until 2035-40.

Mr Johnson also said he was embarking on a massive programme of investment in local transport, including spending £5 billion on buses and bicycles.

He said there will be more than 4,000 new zero-carbon buses and more services in the evenings and at the weekend.

The news was given a qualified welcome by Rob Johnston, chief executive of Cumbria Chamber of Commerce.

The chamber has been campaigning for the HS2 line to use the existing stopping pattern of trains north of Preston, which was backed by West Coast Mainline operator Avanti in December.

Avanti is due to take on HS2 in 2026.

The campaign was launched in response to HS2’s proposals that its trains would operate non-stop between Preston and Scotland, forcing Cumbrian passengers to change at Preston to get to London.

Mr Johnston said: “Improving connectivity is a sure-fire way to boost growth and raise productivity. HS2 certainly has the potential to do that.

“Our concern is that when these high-speed trains join the existing tracks, to continue their journey to Scotland, they won’t stop in Cumbria and we will lose our direct rail service to the capital.

“We’ve been lobbying for more than a year for HS2 trains to observe the existing stopping pattern north of Preston.

“Avanti, the new operator on the West Coast Main Line, agrees with us.

“It would be self-defeating to force passengers between Cumbria and London to change at Preston so we’ll continue to make the case for HS2 services call at Oxenholme, Penrith and Carlisle.”

He welcomed the Government’s pledge to spend £5bn over the next five years to improve bus services and cycling provision.

He added: “Employers tell us that a lack of buses in Cumbria makes it harder for them to recruit staff while high fares deter people from travelling from areas of higher unemployment, such as Barrow, to take jobs elsewhere.

“Bus services in Cumbria don’t receive any public subsidy while in London buses receive £722m a year – that can’t be right. We hope that some of this extra money will find its way here to redress the balance.”

Henri Murison, director of Northern Powerhouse Partnership, said: “The North’s civic and business leaders have argued tirelessly that major infrastructure investment is so badly needed to provide the extra capacity urgently required on our rail network.

"Creating a delivery vehicle to build High Speed North as an integrated high-speed network north to south and east to west, provides the best way to rebalance our national economy and secure the benefits of shared growth in turn, attracting investment in the shortest possible time.

“The Oakervee Review has set out how a process can begin swiftly for HS2 and Northern Powerhouse Rail, to be best configured together with the wider existing network to create a joined up new and upgraded railway for the North – taking up the ambition of the Victorians and being as bold as they were.

"It is the only way we will create the capacity we need to unlock the benefits passengers on packed local trains, get freight off the roads and provide the connectivity which is a pre-requisite of closing the North-South divide for good.

“This a once-in-a-generation opportunity; to create a truly balanced Britain that works for everyone. Integrating HS2 and Northern Powerhouse Rail is the first step – a bold, decisive, forward-looking step that I am heartened the government has finally chosen to take as politicians across both major parties here in the North have campaigned with us for.”

Meanwhile, Matthew Fell, CBI chief UK policy director, said: "The Prime Minister’s decision to back HS2 is exactly the sort of bold, decisive action required to inject confidence in the economy. It sends the right signal around the world that the UK is open for business.

“HS2 shows the Government’s commitment to levelling up the nations and regions of the UK. Once built, HS2 will bring much needed capacity to our railways and help to realise the Government’s promise of an ‘infrastructure revolution’ for the North, Midlands and beyond.

"The time for debate over HS2 is over and the time for delivery is now.”