The boss of HS2 has insisted the high speed rail line will be completed as planned - and will drive up productivity in the regions.
Sir David Higgins said the £56bn project had been supported by three successive governments and repeatedly backed by Parliament.
Some £2.3bn had been spent, the budget for ‘Phase One’ from London to Birmingham had been approved and work had started on the ground.
‘Royal Assent,’ which will give the green light for the eastern section through Yorkshire, is not due until 2021.
But Sir David said he was “100 per cent confident” the project would happen - and bring a host of benefits to the regions.
He was responding to critics who claim it is too costly and disruptive and could eventually face the axe - especially if Britain suffers a post-Brexit downturn.
He said: “There’s an enormous amount of capability and skills in the Midlands and the North, our report identifies that if you improved connectivity it drives up productivity. And Brexit makes it more important than ever.
“I can’t guarantee it will stop the brain drain but we know poor connectivity is why many firms cluster in the South.”
HS2 has produced a report claiming the railway will drive up productivity across the country by slowing the brain drain to London, encouraging face-to-face meetings and collaboration, allowing investors to travel more easily, boosting tourism, increasing international travel by making it easier to get to airports and reducing congestion on roads.
In South Yorkshire, HS2 trains will leave the 250mph mainline and use traditional tracks to reach Chesterfield and Sheffield.
Sir David said: “They will be HS2 trains on an upgraded and electrified line, only an anorak would say it wasn’t a true service. They won’t go 400kmh but they won’t reach that speed on every part of the mainline either.”
New tracks are required to allow trains heading north out of Sheffield to rejoin the HS2 mainline to Leeds.
It is due to be built by Network Rail.
Sir David said it was not in his authority and he could not guarantee it would happen.
But it was a “critical link” in plans for 30-minute journey times between the two cities.
He added: “It’s a decision for the Department for Transport and the Secretary of State.
“Transport for the North says it is a critical link that needs to be built into spending plans. The business case is strong and everyone can see the logic.”
The line is set to open all in one go at some point in 2033.