In the early hours of 9 June 2017, Jeremy Corbyn conceded defeat. For the luckless political journalists forced to cover the Labour campaign this was a rare moment. The leader of the opposition had avoided the press and public. Now, as Labour was going down to its worst defeat since 1935, Corbyn was at last prepared to take questions.

But not before he had made one of the most graceless concession speeches in British political history. He offered no apologies to the scores of Labour MPs who had lost their seats or the millions of voters who needed an alternative to conservatism. He accepted no responsibility. On the contrary, the passive-aggressive Labour leader was as close to jubilation as anyone had seen him. His eyes shone. His voice rang with an unearned self-confidence.

‘You had a responsibility to make sure that the opposition voice was heard,’ he told the journalists, as he blamed them for his failure. ‘Instead of concentrating on policies, you were obsessed, utterly obsessed, with me and a bitter and unrepresentative minority of right-wing critics in the party.

‘But despite all you and your billionaire proprietors threw at us, seven million people voted for a radical socialist alternative to the political establishment. I am not going to let those people down. We now have a Labour movement full of hope. A movement we can build on. A movement that one day will transform Britain.’

As the sense behind his ecstatic ramblings became clear, a BBC political correspondent interrupted. ‘But surely, Mr Corbyn, surely after this disaster you must resign?

Must he? I am a journalist, not a clairvoyant. I cannot see the future, but a few points are clear. Labour’s poll average hovers at around 25 per cent. In a few polls, the Conservatives have opened a 20-point lead. The figures suggest that Labour’s representation will fall from 232 to about 180 seats.

Maybe the losses will not be so bad. Former Labour supporters, after all, will not be driven into the clammy embrace of the Tory party because they fear that Corbyn might actually win. Muscle memory will prompt some traditional voters to put the cross before the Labour party candidate’s name. Others will stay at home rather than support a rival party. Committed left-wingers will vote Labour, of course. Meanwhile, Labour MPs who regard Corbyn as the greatest curse to have befallen their party will have a personal vote among constituents prepared to back them, but not their leader. It need not be a rout, particularly when you consider that Theresa May is a mediocre politician calling a snap election before the problems Brexit heralds become evident.

But think how the Tories will exploit Corbyn’s association with every murderer and gangster from Gerry Adams to Vladimir Putin, then study his own mulish political incompetence, and it is not hard to see the Labour campaign unravelling. It’s not just Corbyn, although we should pause for a moment to honour a party which is offering us a leader in a Brexit election who has nothing to say about Brexit. At a time of national crisis, Labour’s ‘leading lights’ are Emily Thornberry, John McDonnell, Diane Abbott, Richard Burgon and Shami Chakrabarti. I could pick you a better shadow cabinet from a bus queue. In 1935 Labour managed to win just 154 seats. It’s not fanciful to see Labour falling that low, or lower. It is not fanciful to see a polling slump and the vagaries of first-past-the-post turn a party that governed Britain from 1997 to 2010 into a rump. All that can be imagined. Yet I find it impossible to imagine a far left accepting responsibility for defeat and stepping aside.

Its determination to cling on needs clarifying, and the consequences for the opposition our country so urgently requires need understanding. Never make the mistake of using rational explanations to explain irrational movements. If supposed leftists meant what they said about loathing austerity and the Tories who brought it, they would not have voted for Jeremy Corbyn twice. They would now be damning as fools or liars the left-wing journalists who assured them Corbyn would win back Scotland or would somehow turn the millions who do not vote into conscientious, ballot-filling socialists. They would be demanding, even at this late stage, that Labour finds a way to ditch Corbyn and save the country from a Tory landslide.

No such reckoning has taken place. Instead, we have seen test runs for the excuses which will be yelled out on 9 June. It will be the media’s fault, Labour MPs’ fault, anyone and everyone’s fault except theirs. Paul Mason, the closest the left can offer to an intellectual these days, made the template. ‘Nobody can claim losing Copeland was Jeremy Corbyn’s fault,’ he said, after Jeremy Corbyn lost Copeland earlier this year. The country will hear a thousand similarly incomprehensible excuses come June.

It ought to be obvious by now that the prime aim of the left is not to defeat the Conservative party, but to refashion the Labour party. You only have to hear of the insane plan to reselect Labour MPs seven weeks before a general election to know that, or read the outpouring of online hatred against all who cross Corbyn.

Many say that the left is now a cult, which builds impenetrable defences to keep out reality. Few go on to say that, like a cult, it has its true religion. What does it matter to the far left if Labour falls to 180, 150 or 100 seats? The reformist Labour party would still be finished. Labour would be what is has never been in its history, a pure party and a true church where every variety of Chavez nostalgist, post-Trotskyist and conspiracy crank could worship. The Tories cannot rule for ever, the faithful will assure each other. One day the country will break free of false consciousness and turn to them.

Until that glorious day dawns, the task is to maintain control of what will still be the official opposition, however poorly Labour performs. If Jeremy Corbyn were not to grasp that, if he were to step down without guaranteeing that John McDonnell or another comrade could succeed him, his own supporters would denounce him as a traitor. For a man who has accused so many others of treason, that would be an insult he could not bear.

If I am right — and I think I may be — the opposition’s problems do not end with the election. Labour MPs have been keeping quiet in the hope that Corbyn will destroy himself. ‘Jeremy must own this defeat and accept the consequences,’ they say in private. Once the massacre is over, the remnants of the Labour party will find a new leader and begin the overdue task of fighting conservatism. But what if he does not accept the consequences? They could run a candidate against him, as they did before. I know many good people who now regard their support for Corbyn as a terrible mistake, but it is far from certain that they make up a majority of Labour members.

The task of turning Labour into an effective opposition, let alone a potential government, could take a decade to complete — assuming it ever is completed. I do not believe that liberal England will hang around waiting for Labour to go through its ‘learning process’. It’s not just Brexit, although Brexit is mobilising opposition opinion outside parliament to a degree I do not believe the right understands.

May’s authoritarianism and intolerance of dissent, the apparent strategy of shoring up a weakened Britain by turning it into low-regulation corporate playground, the ceaseless bias in favour of the wealthy at the expense of the rest cries out for an alternative now, not some time in the 2030s. Across Europe and north America old parties are withering away. First past the post and the parliamentary system keep ours on life support. You cannot become a senior politician unless you join one and work within its structures.

But for the first time a few Labour MPs are now telling me that if, even after a landslide defeat, Corbyn won’t do the honourable thing and resign, the only honourable course for them will be to form a new party and try to speak to, and for, a country that deserves better than the derisible choice on offer at this election.