After years of hubristic budgets promising to make the neglected north the new Jerusalem, there came something of a change in tone this week: “I’ll try to ensure #NorthernPowerhouse remains a priority,” tweeted former chancellor George Osborne, meekly, from the backbenches.

It sounds as if Osborne knows something we don’t. If you weren’t already worried that our rightwing cabinet has no real commitment to the redistribution of power and money to the north, then you should be now. You don’t have to be a political genius to read between Osborne’s lines: he fears the Berkshire-based prime minister and our Surrey-based chancellor have gone cold on his pet project.

To be fair to him, Osborne was at least a chancellor who talked up the north and recognised the unbalanced nature of our country. He also managed to devolve significant powers away from Westminster. But he wasn’t around long enough to back up all the fine talk and the devolved powers with real money.

One Nation means all parts of country must feel part of our economic success. I'll try to ensure #NorthernPowerhouse remains a priority — George Osborne (@George_Osborne) July 18, 2016

As northern England waited patiently for the much-promised investment in modern rail lines to link our great cities, he used his last budget instead to throw another major bone in the direction of London – billions of pounds for Crossrail 2, even though Crossrail 1 hasn’t even opened.

And let’s not let him rewrite history: Osborne’s period in office saw him inflict the biggest revenue cuts on the north. He used to talk about fixing the roof when the sun was shining. In Greater Manchester, he promised a powerhouse but it has a £1bn hole in it as his public service cuts continue to bite over the coming years.

But Osborne’s northern powerhouse at least held out the promise of Tory jam tomorrow for the undernourished north. Now, with no obvious champion left in government, it looks set to go the same way as the big society: a memorable slogan leaving no discernible legacy. The emphasis on PR rather than end-product seems to sum up the Cameron-Osborne era.

A week into office, the new PM and chancellor have yet to give any public statement of support for the northern powerhouse. All of a sudden, it feels distinctly out of fashion. But if they are going cold on it, the new government will be making a monumental political mistake – and entirely the wrong response to the EU referendum. The truth is that, in post-Brexit Britain, the northern powerhouse should become much more, not less, important.

Osborne is an astute politician. He had correctly identified a growing and dangerous alienation from politics in many parts of the north. The strong leave vote in former industrial areas didn’t just reflect concern about immigration, as some would claim; it was a howl of protest over decades of neglect by governments of all colours.

For too long, we have lived in a centralised country where the London perspective has dominated the political debate. Consequently, policy solutions have been designed for the south and not the north. All the while, the gap between the two has grown.

Take education policy. For a long time, under all governments, the focus of national policy has been on universities. Unlike Germany, where academic and technical routes are seen as equals, there has been a longstanding snobbery in England towards technical education. By measuring school performance on A-C grades at GCSE, our education system invites schools to devote more attention to university-bound kids than to those who want something else. This blinkered policy approach has been damaging for young people everywhere, but particularly those in our former industrial areas.

Or take housing. Here, again, the concerns of voters in mythical Middle England had led to a focus on promoting owner-occupation over and above everything else. In the more deprived parts of the country, that goal was never realistically going to be within the reach of everyone. What was needed was more council and social housing. But councils have been prevented from providing this by policy edicts from Westminster. Consequently, many people in the north are trapped in poor quality, overpriced rented accommodation owned by absent landlords.

Or, lastly, take industrial policy – or the lack of it. For a long time, Westminster has obsessed over the “knowledge economy”, or the service sector, and neglected manufacturing. In the last 30 years, traditional industry has been allowed to disappear from many parts of England without any significant help for those areas to regenerate and diversify. It is a scandalous unfairness.

Westminster’s failure to provide answers for many parts of the country on these three crucial issues explains the roots of the backlash that we felt on 23 June. Yes, immigration was a major concern. But it is in effect the lightning rod for a much deeper current of anger at the political system.

As part of the Brexit debate, there needs to be real progress on this. If I am the first elected mayor of Greater Manchester, I will use devolution to place a new emphasis on technical education, council housing and advanced manufacturing.

If the government goes cold on the northern powerhouse, and fails to show these areas that it has listened and understood the message they sent, then the political crisis in our country will only deepen.

If the new PM wants to make good her welcome promises about closing the divides in our society – and fighting the “burning injustices” – she must back it up with real money and fully embrace the northern powerhouse project. In fact, she should go much further than Osborne ever did.

I am writing to her today to ask her to do just that and setting four key challenges.

First, we need to hear an early statement of support from her and her chancellor for the whole northern powerhouse concept. The silence is making people suspicious.

Second, she should make a clear commitment that the more neglected parts of our country will not lose out from Brexit. Over the years, having struggled to get money out of Westminster, many have succeeded in prizing structural funds out of Europe. Already, Greater Manchester is predicting the loss of £320m in EU structural funding up to 2020. Theresa May should ask the Treasury to make good any potential losses.

Third, she should make investment in east-west rail across the north linking our great cities the country’s top transport investment priority. Our train services are light years behind London. It simply cannot be the case that Crossrail 2 is the highest priority for transport investment in our country. I have heard rumours this week that the government is looking to prune back elements of the HS2 scheme, which will close down options for HS3. That cannot be right and May needs to rule out any possibility of it.

Lastly, she should say that, if the right ideas come along, she is prepared to take devolution in England much, much further. One of the biggest missing pieces in the Greater Manchester devolution deal is the Department for Work and Pensions budget. I am certain that, if we had control of it in Greater Manchester, we could do far better than the cruel, tick-box, sanctions-based DWP regime. By linking it to our community and voluntary groups, and breaking down the silos with other public services, we could spend it better and help more people get on.

Far from leaving the northern powerhouse to go to rack and ruin, now is the time to start planning an extension.