For the best part of three years, Britain has been stalled at a political T-junction. Last night, the electorate put their foot down and yanked the steering wheel to the right. They didn't bother to look where they were going, and we will all now suffer the consequences.

The Conservatives gained an avalanche of seats in small, socially-conservative towns that were once Labour's heartlands. Labour held only the cities and big towns. The same crisis that's ripped through centre-left parties across the world – driven by a mismatch between their values and those of elderly white working class people – has hit Britain.

The stark results have to be digested quickly by a young generation, who see the Conservative Party as close to poison.

First: Brexit will happen. It will happen fast and its impetus will be towards radical deregulation of our society.

It may produce some economic chaos, or the severe erosion of the welfare state, but from now on the right-wing Tory government – in an implicit coalition with the Brexit Party – will have a ready excuse: the foreigners, the Europeans, the left, the saboteurs, the judges. These are the new public enemies we will be invited to hate. Everything that goes wrong with Brexit will be laid at the door of those who opposed it.

Second: a new Scottish independence crisis will open up. You cannot rule a nation of 6 million people who want Europe, social justice and national independence with a viceroy from London. The SNP's old demand was for a second independence referendum by 2021. By the standards that used to apply in international law, they hardly need one. If 55 of 59 Scottish MPs are independentists, the moral case for self-determination is already there.

You may be wondering how this slam-dunk by the right against the left happened. To me, it's simple. We're facing an alliance of the mainstream right and the far right: what the philosopher Hannah Arendt called "the alliance of the elite and the mob".

Every lesson from the 1930s tells us: the only answer to this is an alliance of the centre and the left. But survey the results and it's clear the centre and the left did not want to ally. They wanted to rip each other to shreds.

In London's Kensington, the scene of the Grenfell fire, the Conservatives retook the seat from Labour because 9,000 votes went to an ex-Tory adopted by the Lib Dems. In seat after seat, Green candidates stood beaming as their scant 1,000 votes meant the difference between a right-wing Tory and a socialist, including the stellar Labour left-winger Laura Pidcock in Durham.

For Labour, the main task was to stop this election becoming a referendum on Brexit. And they did – but only among their loyal supporters. On the doorsteps, young working families eagerly took our leaflets and posters – even in the towns we've lost. For the right-wing half of the population – actually numbering around 45 percent of the national total – it was always and only about Brexit, migration and English nationalism.

I expected Labour to lose, but not this badly. Given Corbyn's unpopularity and the newness of Johnson it was always going to be an uphill struggle. The shocking thing is that, almost without a machine or any campaigners, the Tories took historic Labour towns, because the vibe was on their side.

That vibe was best summed up by a man who approached me in the high street of Leigh, where I grew up: "I'm not allowed to say what I want..." he began. We coaxed it out of him. "I want Boris Johnson to send people round to the homes of every Romanian and throw them and their kids in the back of a van, lock the door and drive them to Dover."

That is the world you now live in, and all the grime artists and comedians who supported Labour count for nothing. The entire street in Coventry I canvassed, where mainly Muslim families raised their thumbs through the front window – to save opening the door – count for nothing.

If Brexit is the worst outcome of this I will be relieved. With a large majority, Johnson is now free to redraw the electoral map, making a Labour majority government impossible. In fact, as demonstrated for the third time running, it is probably impossible anyway, because Scotland has moved permanently to the SNP and may soon leave the Union. The real danger is that we become a "managed democracy" – with a rigged electoral system, a sham judiciary and a compliant state broadcaster. There will still be elections every five years, but only one party can win them.

I've supported Jeremy Corbyn, and I'm proud of the way he stood up to vilification, dragged the party strongly onto the agenda of climate change and fought Brexit. Brexit was always a right-wing, xenophobic project – it would have been easy for a traditional Labour leader to go with the flow, throwing migrants and democracy under a bus. Corbyn understood that to support the Tory Brexit was suicide: those MPs in Stoke and Doncaster who did so paid the price just as badly as those who opposed it.

But we have to move on from Corbynism. I'm supposed to be one of its architects, but I never liked the label. I'm a radical social democrat, committed to an open migration system, tolerance of minorities and to pursing social justice alongside economic justice. Too many of my Labour comrades were simply nostalgic for the post-war system, and some even for the Soviet Union.

As a result, once the Brexit crisis hit, we had to fight each other before we could design a coherent Labour policy – and I don't think Corbyn ever enthusiastically sold that policy to the electorate.

Labour's future has to remain on the left. There can be no going back to the economics that devastated the community I come from, and no return to support for imperialist wars and torture. But it has to evolve.

In this election campaign, tens of thousands of ordinary young people learned to do politics. Twenty-four hours ago I was at Euston station seeing young activists filter through to all points north, to go campaigning: Milton Keynes, Northampton, Birmingham. We've never seen this level of activism, driven digitally, so we didn't know what impact it might have.

The answer is probably none – because we were up against prejudice, exhaustion and a juggernaut of fake news. But that activism is the key to the future.

Labour, whatever else it does, will become the resistance. I think the party can and should grow from half a million people to a million, and I invite you to consider joining it. The small centrist parties formed in the past 12 months have disappeared from parliament and the Lib Dems have shrunk. The main three forces in British politics are still Labour, Scottish Nationalism and the Tory/Farage alliance. Plus, of course, the people – who've been on the streets in numbers greater than a million to resist the Tory Brexit.