Since last Thursday, my inbox has burned with anguish about the state of our nation and our politics. People fear splits that are not just geographical, but also between generations and income groups. These divisions exist everywhere – while I’m proud that Walthamstow voted two to one to stay in the EU, locally and nationally our success will depend on finding ways to rewrite what at present looks like a very bleak future. To stop despair curdling our capacity to achieve this, Labour must urgently offer a radical and distinctive response.

It would be easy in such circumstances to lapse into misery; to find someone or something to blame – and luxuriate in the safety of opposition believing a scapegoat is enough. But now is the time to recognise our hunger for social justice demands we do more than wring our hands; not to think in abstracts, but to focus on finding direct and deliverable answers to the challenges we face. And above all, to stand for something, not just against something. To be against austerity, neoliberalism or corporations: this only describes what you want to stop, not what you will achieve. Hold a placard, tweet a slogan, buy the T-shirt if it helps, but if you want real change you have to be prepared to work at making it happen in detail as well as in hashtags.

Britain is crying out for progressive and courageous change-makers to help put it back together. We need leadership which, in the negotiations ahead, knows why we fought to protect the rights we could lose by leaving the EU. We need leadership that also looks to the world to come and champions how we can co-operate across our communities, our country and our continent. At a time of whirlwind global economic change and social disruption, the UK has just set out its intent to cut itself off from the collective bargaining power of the European Union. Leaving or staying is no silver bullet – it only increases or reduces our options for action. With Britain this badly broken, we cannot shrink into holding repeated meetings about how we wish it were different. In an era when money, services and people move at rapid pace, the crisis Labour faces is about its very purpose, not just its people. We have to show we can lead the way in the world to come, not the world gone by.

Labour must again be a progressive party which has courage. Courage to say the world is a very different place and so our answers must change too – including from those given by any previous Labour administration. To give everyone a real chance to succeed, our vision of the economy, of our public services, indeed, of our core mission, needs to be completely revised – less focused on institutions, more rooted in networks of people working together to transform markets and communities than anything ever previously proposed. Not a movement trying to stop the pace of change, but one actively trying to hasten and shape it for the benefit of all.

This would be hard work at the best of times; Labour is a party running on empty, with energy and ideas as well as organisation depleted. We have never been a cult, where everyone has to think the same or leave. As grown-ups, we are able both to have differences of opinion and to make compromises so together we can take action. Actions that every day show we seek power to speed up and strengthen our ability to achieve our goals – and that we also refuse to wait until we hold office to get started on our ambitions for Britain.

I have never agreed completely with any leader – whether on ID cards, going to war in Iraq or skirting the Financial Transaction Tax – but I have always fought our corner. Labour needs each of us to put our very all – our 10 out of 10, not 7.5 – into achieving our aims. Each of us asking the public to take sometimes difficult steps with us because we believe it is in the best interests of the country. That is why I have no confidence in Jeremy Corbyn any more. It is unforgivable to have a leader who, when faced with Brexit and the damage it could do, asked others to go on to the pitch while he benched himself.

Being half-hearted about key issues in a world this complex and challenging does little for those we care for most or to win the argument for progressive outcomes – as is now depressingly clear. The trolls and naysayers will stamp their feet whatever happens; it is our responsibility to chart a different course. Labour doesn’t just need new leadership, but also new passion and determination for social justice and social action. As these forces try to tear us apart, let us reject the politics of inertia. Let each of us work to bring Britain back together to face the 21st century with confidence, commitment and common cause.