Brexit Britain is right. The status quo is insupportable. But the solution is not to leave the European Union. Our problems are made in Britain; they can only be solved in Britain. Europe does not impede this mission; rather it is indispensable. The imperative is to transform the way our country works.

The poverty, inequalities and hopelessness that propelled the Brexit vote – seven out of the 10 poorest areas in northern Europe are in England, and all voted for Brexit – must be decisively addressed. Britain must simultaneously recommit to full EU membership as its benefits and the colossal costs of exit become ever clearer, and stand solidly with Europe as dark and menacing forces stalk the globe – not least an imminent transatlantic trade war and the wider threats of Donald Trump.

To chase the economic moonbeams peddled by Brexiters while the values we prize are under global assault, to cower behind borders that shut out the rest of our continent, and to seek to resurrect an unachievable island sovereignty: this is a dead end that can only result in widespread suffering. That could even begin the day after Brexit next year, with widespread shortages of medicines, fuel and food as the port of Dover collapses with no Brexit deal – according to Whitehall departments’ risk assessments leaked and paraded in the Sunday Times yesterday.

Brexiters dodge these truths. Intent on completing the Thatcher revolution, they want us out of the EU at any cost. While feigning concern for the state of Britain, their real agenda is wholly to embed a Thatcherite world of self-organising free markets and minimal social provision that will bring unalloyed benefit – whatever the baleful track record. They want out of Europe because it stands in their way.

But two years after the referendum, the Brexiters’ “have your cake and eat it” fantasies have evaporated. There is no Brexit dividend, rather the prospect of dismal economic growth and tax rises. The extra £350m a week supposedly available for the NHS turns out not to exist and instead we have an exit bill of £39bn (and rising). Then there is the up to £20bn a year cost of observing customs obligations after Brexit – an avalanche of self-imposed red tape – along with as much or more again as UK organisations expensively relocate to the European mainland.

Virtually no one still claims, as they did during the referendum campaign, that we can retain the economic benefits of EU membership while leaving the European customs union and the single market. The prospect of “quick and simple” trade deals outside the EU is now recognised as delusory, particularly with Trump’s protectionist US and Xi Jinping’s China. It is the “global” EU that already has the trade deals, either done or in the making, with at least 60 countries, including Canada, Japan and South Korea – which are all in jeopardy for the UK on Brexit day. The EU is the citadel of rules-based international free trade and the international standard-setter that Britain did so much to create – and at whose centre we stood. “Global Britain” is a chimera.

The economic warnings are there for those prepared to see them. Inward investment has collapsed by some £130bn over the last 12 months. The car industry fears “Carmageddon”. There is no open-skies deal with the US. Being frozen out of the Galileo project endangers our space industry. Universities fear being cut out of EU research budgets. It is the same in sector after sector.

‘Two years after the referendum, the Brexiters’ “have your cake and eat it” fantasies have evaporated.’ Photograph: Jack Taylor/Getty Images

Europe’s achievements have not been driven solely by an economic calculus: they belonged to a bigger, nobler cause of representing European values, rooted in democracy. This is why any form of Brexit is a mistake. We want to share a continent where Europeans don’t fight each other, don’t prevent trade and where we allow its people to live and work wherever they like across their region. Never has Europe been so peaceful, democratic and prosperous as in the era of the EU.

But too much of Britain was hurting for it to hear this message, inflamed by fears over immigration. The 30 social mobility “coldspots” identified by the Social Mobility Commission all voted Brexit. So did areas where property prices were stuck, where life expectancy was falling, where antidepressants were widely prescribed and where life chances were thin. In too much of the UK beyond London and the south-east, economic performance is mediocre or downright bad. The social contract has become for many people effectively nonexistent. Unemployment may be at a 40-year low, but so are savings to maintain living standards: insecure, poorly paid work is at a record high. Real wages are 7% lower than they were at the time of the financial crisis – an unprecedented squeeze. Of course immigration seemed menacing.

Saving Britain is a twin-pronged task: transforming our economy and society so they work for all while recommitting to an EU that covers our backs better than we know. Today’s laissez-faire, sink-or-swim approach to economics and society has to end; instead our hijacked capitalism must be populated with repurposed businesses, motivated by a desire to produce goods and services that better humanity. New technology needs to be mobilised for the public good, while great institutions that serve the mass of people – such as trade unions, public-benefit companies to run utilities and building societies – must be reinvigorated and reshaped.

A refashioned social contract should invest public money where desperately needed and raise the necessary taxes fairly. The centrepiece should be an educational Marshall plan. Part of this contract should be a stronger notion of citizenship, including a national identity card system to assure citizens that we know exactly who is here and what they are entitled to.

A Great Charter for Modern Britain would hand power from Westminster to the cities, towns and counties of Britain so as to transform their localities, represented in a senate to replace the House of Lords, located in the north of England. This should be the foundation of a fully fledged written constitution.

It is the Labour party – firmly pro-European and credible in its commitment to social reform – that could rally the country. The present policy of colluding in Brexit, while trying to make sure it is a Tory-authored disaster, will impose unnecessary suffering on too many. The great power of democracy is that citizens can change their minds as facts change: the Brexit refusal to countenance a second vote on grounds of its divisiveness is born of fear that the people will reassess their decision. The worse divisiveness is to press on regardless.

Great countries find the political resource to turn around epic mistakes. The Labour party has the chance to save Britain, stand by Europe at a critical juncture in world affairs and form a great reforming government. It is an opportunity that must be seized.

• Saving Britain by Will Hutton and Andrew Adonis is published by Abacus, price £8.99. To order a copy for £6.99, go to guardianbookshop.com