A minister will be appointed to oversee HS2 full time, Boris Johnson has announced, as he confirmed he was giving the project the go-ahead.
Speaking in the Commons Mr Johnson said his cabinet had given the project the “green light” despite fears over its cost and impact on the environment.
Mr Johnson said his Government had a choice between “trying to get by with existing routes from North to South” or having “the guts to take a decision, no matter how difficult”.
And to those in his party who had publicly called for Northern Powerhouse Rail instead of HS2 Mr Johnson said “this is not an either or proposition”.
He said: "Some have suggested delaying or even cancelling HS2 in order to get Northern Powerhouse Rail done more quickly.
"But I want to say to you, Mr Speaker and to the House, this is not an either-or proposition. Both are needed, and both will be built as quickly and as cost-effectively as possible.
"And to make sure that happens we will, working closely with Northern leaders, explore options for creating a new delivery vehicle for Northern Powerhouse Rail and we will start treating the HS2 north of Birmingham, Northern Powerhouse Rail and other local rail improvements as part of one integrated master plan High Speed North."
Mr Johnson said that "those who say we should simply build phase 2B and Northern Powerhouse Rail according to the plans currently on the table are effectively condemning the North to get nothing for 20 years" which would be "intolerable".
However the PM took aim at HS2 Ltd, the organisation tasked with delivering the project, and he said to avoid "further blow outs" in cost or schedule, a series of measures will be taken to "restore discipline to the programme", he said.
He told MPs: "When it comes to advocating HS2, it must be said that the task is not made easier by HS2 Ltd, the company concerned.
"Speaking as an MP whose constituency is on the route, I cannot say that HS2 Ltd has distinguished itself in the handling of local communities."
He added: "But poor management to date has not detracted, in my view, from the fundamental value of the project."
New measures will include appointing a minister whose full time job will be to oversee the project, and changes to the way HS2 is managed.
He added: "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."
Mr Johnson added: "This is not just about getting from London to Birmingham and back.
"This is about finally making a rapid connection from the West Midlands to the Northern Powerhouse, to Liverpool, to Manchester, to Leeds and simultaneously permitting us to go forward with Northern Powerhouse Rail across the Pennines - finally giving the home of the railways the fast connections they need.
"And none of that, none of it makes any sense without HS2."
He added: "The Infrastructure and Projects Authority considers that this first phase can be delivered for its current projected costs of £35bn to £45bn in today's prices."
Mr Johnson said: "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. We are going to get this done.”