Jeremy Corbyn's re-election is a disaster for Labour. In 34 years of watching Westminster, I have never seen a party so riven

When Jeremy Corbyn’s critics launched their challenge to his leadership after the June EU referendum, they thought it would weaken him even if it did not topple him. But his increased majority – up from 59 per cent last year to 62 per cent – has only strengthened Corbyn. His bigger mandate is a disaster for his Labour opponents.

With hindsight, they should have given him longer – perhaps two years – to show whether he was up to the job. Many members judged that he was not given a fair chance by Labour MPs. Even some party members who doubt Corbyn’s competence stuck with him because they feared that ditching him would hand Labour back to the party’s discredited establishment. Corbyn’s critics underestimated this strong desire to avoid a return to the New Labour era. These members would rather gamble on something different, even if there is only a slim chance of returning to power under Corbyn.

In his victory speech, Corbyn urged his critics to “respect the democratic choice” of the party. He tossed a bone to his opponents by declaring that “intimidation and abuse” was not his way or Labour’s.

Although both camps will talk the talk about unity, it will be very hard to make Labour’s truce stick. In 34 years of Westminster-watching, I have never known a party so riven. The gulf between Team Corbyn and his MPs is so wide that it is unbridgeable. We now know that the members overwhelmingly still back Corbyn.

It is very doubtful whether Labour’s two parties – the Corbyn-led members’ party and the MPs' one – can be merged back into one. Corbyn will reach out to MPs, and try to persuade the 62 who quit frontbench positions this summer to return, so that he has a credible team rather than lots of empty chairs and unknown figures juggling more than one job. Some MPs will come back, but others will remain in the refusenik camp.

If he was serious about reconciliation, Corbyn would agree to return to the system, scrapped by Ed Miliband, under which MPs would elect the Shadow Cabinet. But he is unlikely to do so as he could then be outgunned on policy, so his writ would not run. Once the left gets its hands on the levers of power, it does not hand it over to its opponents. So the Shadow Cabinet issue is likely to be kicked into the long grass of a wider review of party democracy. Team Corbyn’s aim will be to give more power to party members, further diluting the influence of MPs.

It is going to be very difficult to put the pieces back together again and create a stable opposition. Too much blood has already been spilled. MPs who do return to the front bench will be quizzed constantly by the media why they were among the 80 per cent of Labour MPs to declare they had no confidence in Corbyn. They will be asked whether he is fit to be prime minister. “We will just have to tell a lie,” one MP admitted. Such doubts about Corbyn’s ability, even if kept private, are bound to filter through to the public.

Mainstream Labour MPs also want Corbyn to end talk of them being deselected by their constituency parties before the general election. Corbyn aides insist there are “no plans” for such a purge. But that will not reassure MPs who feel under threat: there don’t need to be any plans. Changes to Parliamentary boundaries will give left-wing members the opportunity to replace MPs with one of their own. The Corbyn support network Momentum is bound to use its growing strength to make this happen.

MPs also want to see an end to what they call the “us and them” culture of Corbyn’s leadership. Some who tried to make it work by serving under him complained of a dysfunctional operation in which those who did not agree with him were sidelined. They want a real say over policy, rather than a top down approach by the leader’s office. They also want to see Corbyn engage with the real challenges facing the country – notably Brexit, which he rarely talks about and has not raised at Prime Minister’s Questions.

Perhaps there is a third way – even though Tony Blair is so hated by the Corbynistas that nobody will use that label. The compromise could be that most MPs rally behind Corbyn for now, to give him a chance to show he can win over voters without the constant threat of being ousted by his party. There would then be a “review” of whether Corbyn is the right man to lead the party into the next general election. The idea has been floated by Andy Burnham, the shadow Home Secretary, who said no one has the right to lead the party to a catastrophic election defeat.

Any truce will probably be short-lived, a mere pause in Labour’s civil war. Many of Corbyn’s critics are in no mood for compromise. Although a formal, SDP-style breakaway is unlikely before a general election, some MPs plan to remain a semi-detached group, which will be seen as the “shadow Shadow Cabinet.” There is talk of another leadership challenge next year, which would be the third contest in three years. But this year’s election showed that Corbyn’s critics do not yet have a credible candidate and so there might be little point in making the same mistake next year.

Labour’s real problem is that, after his overwhelming victory, Corbyn will be tempted to devote his energies to building the social movement which has grown in strength during the leadership contest, rather than creating the effective opposition the country desperately needs.