If the United Kingdom is to survive, it will have to change fundamentally, so that Scotland does not secede and our regions can once again feel part of it.

The shift in votes that gave the Conservatives an 80-seat majority does not signal a country at ease with itself or settling down to a post-Brexit stability. Nor does it herald a newfound unity or even an emerging national consensus.

Recent events are better understood as resulting from the power of competing nationalisms: Brexit nationalism, seeking national independence from Europe; Scottish nationalism; Welsh nationalism; and Irish and Ulster nationalisms. The risk is that “getting Brexit done” is leaving Britain undone and, by destabilising the careful balance between the Irish and British identities in Northern Ireland, threatening the very existence of the United Kingdom.

While each nationalism considers itself unique and incontrovertibly powerful, their rise owes far more to common problems shared in every part of the UK: anxieties about stagnating incomes, the rundown of manufacturing, insecure employment, poor-quality public services, boarded-up high streets, a lethal cocktail when combined with a strong sense of cultural loss and of a globalisation that seems akin to a train that has run out of control.

How often do we hear people saying “our country is not what it used to be” and that “it has changed beyond recognition”? With that comes a breakdown in trust (“they’re all out for themselves”) and demands to “take back control”, with both main parties seen as out of touch and easily accused of being patronising London elites who act as if the man in Whitehall still knows best.

In this respect, last month’s election result seems less like an enthusiastic endorsement of any party than a plea for radical change. The old postwar social contract, based on times when manufacturing, making a product in which you had pride, and mining which kept the nation’s lights on, gave people dignity and respect, is seen as at breaking point, with each of its four pillars approaching collapse.

First, for millions, work no longer pays. Second, no matter how hard many strive, opportunities for upward mobility seem limited. Parents no longer feel confident that the next generation will do as well as the last. Third, with boardroom excesses, a bankers’ bonus culture and shocking inequalities in income, top people’s pay can never again be justified as the result of merit and hard work. Finally, our 75-year-old safety net looks threadbare when in every town and city child poverty and homelessness are rising and food banks, clothing banks, bedding banks, baby banks and other charities are substituting for a welfare state in retreat. All of this is magnified by the growing income and wealth gap between London and the north that is far more extreme than in almost every European nation and the US’s richer and poorer states. There is an ever-widening divide in how people perceive their future: how, the further you are from the centre of power, the more you feel undervalued and unfairly treated. Only as NHS patients do people feel treated as equals, though there are increasing regional and social class disparities.

This widespread and rising dissatisfaction is the context for today’s populist nationalisms. The 19th- and 20th-century nationalism that underpinned anticolonial movements and the breakup of the imperial dynasties was driven by anger at cultural discrimination, political exclusion and the economic exploitation of one ethnic group by another.

A woman at a food bank in Northampton. Photograph: John Robertson/The Guardian

But the nationalisms we are now witnessing have different origins; at a time when class, religious and even local loyalties have become less salient, nationalists are successfully leveraging economic insecurity, cultural fears and an anti-politics sentiment. Yet none of these grievances can ever be answered by simply changing our borders or raising new flags – or by the act of leaving the European Union.

Nationalism can exploit these injustices but it cannot end them. While the Conservatives are the current beneficiaries of the revolt of the regions, their promise of a northern renaissance will have to mean more than love-bombing the regions with a few infrastructure projects and an airline rescue.

Instead, we must deliver a radical alternative to nationalism. It must start with a plan to address economic insecurity. But it must also recognise that, in a multinational state that is asymmetric (83% of its voters lie in one nation) and where financial, political and administrative power is concentrated in just one city far to the south, the outlying nations and regions require new powers of initiative as decision-making centres – which, given our history as a unitary state, would be something akin to a British constitutional revolution.

I would call a constitutional convention, preceded by region-by-region citizens’ assemblies to listen closely to what communities are thinking and aspire to. But a start could be made with a forum of the nations and regions that will become essential if transferring decision-making powers out of Brussels is not to lead to even more centralisation in Whitehall, and could be a forerunner for a very different second chamber.

The Treasury should also devolve decisions about the allocation of regional resources to new councils of the north and Midlands, comprising mayors, councillors and MPs. With proper financial backing, whether in research, science, technology, new industries or culture, cities and towns in every region – not just London – could become leaders for the UK, capitals in their own right.

If the government won’t act, the regions and nations should mobilise their collective power. For now, it is easy for a PM to prioritise the claims of the centre over any one area. But if Scotland, Wales, Northern Ireland and England’s regions come together as a pressure group for a “Britain beyond the south-east”, their demands could become irresistible and each would carve out a new role and status within the UK.

When George Orwell made the distinction between patriots who love their country and nationalists who see life as a constant struggle between an “us” and a “them” and invent enemies – and grievances – where none exist, he called for a “moral effort” to defeat nationalist ideologies.

In 2020, that means rediscovering the value of empathy and solidarity between nations and regions and the benefits that can flow from cooperation and sharing in pursuit of great causes: from jointly tackling climate change to offering the same floor of rights to universal health, social care and welfare services in every part of the UK.

Only then will we start to prove that the United Kingdom is united by more than its name.

• Gordon Brown was prime minister from 2007 to 2010