Henri Murison, director of the Northern Powerhouse Partnership, told the 2021 Great Northern Conference that ministers had yet to fully realise the potential of devolution to the English regions and that the north was ideally suited to delivering economic renewal for the whole country. However he said a lack of support for levelling up was "holding back the agenda and holding back the north of England".
Mr Murison also said that the uncertainty concerning both HS2 and Northern Powerhouse Rail was hampering investment into the North of England and urged the Prime Minister to be bold in the forthcoming Integrated Rail Plan.
"It is my contention that without the Northern Powerhouse, the Government will not be able to make the offer of levelling up," he said.
"We can rebalance the economy so London and South East will not longer be the principal driver of UK plc."
The NPP director said that the North was ideally placed to lead on growth industries such as green energy and healthcare. But he said further investment in skills was key to realising this and that devolved regions in the north needed more responsibilities.
"We do have significant powers but need significantly more," he said.
"There is a clear case for mayors to take more responsibility.
"Central Government has not recognised the full potential of what devolution can deliver for this country and believes its own priorities should be delivered from Whitehall rather than working with the north of England.
"I hope that Michael Gove changes that attitude."
Mr Murison said that the plan for the Northern Powerhouse, first laid out more than six years ago by then Chancellor George Osborne, provided the blueprint for a fairer country and that this needed to be backed.
He added: "It falls to this Government to not simply see the towns of the north of England as seats to be fought over, but as a place that wishes to come together to help rebalance the economy.
"My challenge for this Government that their roadmap is as comprehensive as what we have, otherwise conference we should stick with the one we have."
On the delayed Integrated Rail Plan, Mr Murison said: "The challenge of having delay and delay on big decisions on things like HS2 and Northern Powerhouse Rail is creating uncertainty for investors.
"For those who are building and investing in the South Bank of Leeds to double the size of the city centre, what message does it send that Government cannot even decide whether HS2 trains should go to Leeds.
"What message does it send to people in Bradford, Warrington and Liverpool that we are not clear with them as to whether they should be able to access the high speed rail networks that exist in the cities of Manchester and Leeds? Why can't we give them that uncertainty?
"I do hope that the Government will represent an integrated rail plan that will be as ambitious as the Prime Minister has always said it would.
"And I urge the Prime Minister to follow his own best instincts and to be brave to introduce an integrated rail plan that takes advantage of the huge potential of the north, rather than be limited by an historical grudge to development in this part of the world.
"The reality is we have not built a major new railway in the north of England since Victorian times."
He also called for more devolution into the north, mentioning both North Yorkshire and the area north of the Humber.