Tomorrow, the United Kingdom will leave the European Union. Some will celebrate, some will mourn, and others will just get on with their lives. The debate over whether we are in or out of the EU is over, but the debate over the kind of country we want to become has only just begun.

As a country we’ve been bitterly divided for three and a half years. Our politics has been frozen instead of tackling the real and deep-rooted problems we face.

Now the leave-remain divide must end. Defining people by how they voted in June 2016 merely upholds a divide that we must overcome. There are no leavers or remainers any more. In 2024 there will be no leave or remain constituencies.

This morning, in a typical classroom of 30 children, nine of them will be living in poverty. The morning after we’ve left the EU, this will still be a reality for those children and their families. It will be the same in a year’s time, and a year after that, unless we do something. The Conservatives are using the rhetoric of sovereignty as cover for the systematic disempowerment of all of us – ever lower wages, fewer workplace rights, weaker environmental protections. Inequality is not an act of God or nature – it is the result of political decisions, but we can change them if we choose to.

Brexit will not put right the problems that led so many to vote leave. They are the result of years of failure, which we will put right only when we stop diagnosing and start treating. We can fix the broken political system that closed off investment and opportunity to whole regions and communities. We can take on the failed market economy that has pushed millions into poverty. We’re not the luckless victims of the unimaginably wealthy. But power concedes nothing without a demand. We can make those demands, because we know what is needed to create the country we want to live in.

We must raise our sights with a vision that matches the ambition of the British people

Seventy-five years ago Britain’s great generation won the war, helping to free occupied Europe and liberate the concentration camps. They dreamed of a better future and they trusted Labour to “win the peace”. That Labour generation rebuilt our country after the devastation of war and created a new settlement that lasted for generations. The NHS, the welfare state, decent affordable council homes, the promise of the new towns and civic pride and placing great industries and national infrastructure under democratic control: this was their achievement and it created a better life for millions. Our present Labour generation must summon that same spirit of courage and radicalism to “win the peace” again after the divisions of Brexit.

It’s clear our politics is broken. This week I’ve travelled the length and breadth of the UK talking about radical plans to devolve power away from Whitehall to the nations, regions, cities and towns. But this can’t just be about transferring power from one set of politicians to another. I believe the fight for social, economic and climate justice can only be won if we put real power directly in the hands of the people.

The market economy has failed and left millions in poverty. Under privatisation our probation service does not work, our railways do not work. I want new forms of common ownership that give frontline workers and the people who use our public services the power to influence how they are run. Real democratic accountability to the people, not statism.

The green new deal must be hardwired into everything we do because we’re in an epochal battle to save our planet. That means a major role for government in stronger regulation and redirecting investment. It also means empowering communities and activists to take action for themselves, like Labour-run Plymouth council has done by setting up dozens of community-owned sustainable energy co-ops.

And I want to scrap the Tory welfare reforms that humiliate the very people they should be helping. I will end the cruelty of work capability assessments and halt the punitive sanctions that push people into destitution. Instead, people who are unemployed or living with disabilities will have a say over the kind of support they need. A real voice for everyone and the power to make it heard.

Britain is an outward-looking country with a proud history of internationalism and co-operation. When Boris Johnson decided last week to turn away child refugees, he stood in the face of those values. Instead of this, the government ought to begin to heal divisions. We need long-overdue security for EU citizens. The government should give all 3 million EU nationals living in the UK full voting rights in future elections. The way they have been treated over the past three years is shameful. We were never just “tolerating” EU citizens living in this country – they are our neighbours, friends and families. To see their status in doubt devastates our sense not just of justice but also of fellowship.

Basic social justice demands that we always stand up for citizens’ rights and oppose trade deals that put our NHS or public services up for sale. We must make the case for a close economic relationship with the EU that protects jobs and allows us to cooperate in other fields.

We’ll shine a light on the Conservatives’ failures and the damage they will inevitably do. We must raise our sights with a vision that matches the ambition of the British people. We must summon the courage that led Labour’s post-war generation to remake this country with a radical vision of a fairer future.

Labour has lost four elections in a row: we simply cannot afford to lose the next one. I will move our party on from the division of the past and remake our party as a democratic movement that faces outwards towards the country, not inwards on itself. Endless Conservative government is not inevitable. I’m here to lead Labour to victory because I know that another future is possible if we come together and fight for it.

• Keir Starmer is the MP for Holborn and St Pancras and a Labour party leadership candidate

• Guardian Live Event, Labour leadership hustings: Join us in Manchester on Tuesday 25 February for a live debate with the four candidates vying for the Labour party leadership. Our chair, Anushka Asthana, will put questions to the candidates Keir Starmer, Lisa Nandy, Rebecca Long-Bailey and Emily Thornberry. Book tickets here