Charlatan Boris Johnson looks set to win the Tory leadership on the basis of his declaration that the UK must leave the EU by 31 October, “do or die”. Some claim he’s merely crowd-pleasing and that, in Number 10, he’ll be transformed into a mature statesman. That is nonsense. Johnson knows that the Brexit party represents an existential threat to the Conservatives, and that the only way to burst the Farage bubble is to deliver Brexit. His two overriding priorities will therefore be to avoid extending article 50 and to ensure there is no general election while the UK is still an EU member.

We are therefore staring down the barrel of a catastrophic no-deal crash-out, which will do the greatest harm to the most fragile communities, compromise our national security and shake the precious Irish peace process to its foundations. MPs can huff and puff all they like, but they are powerless now that the mechanisms used to seize control of the order paper are no longer available. Tory MPs talk about being prepared to overthrow their own government, but will they really usher in a Jeremy Corbyn premiership?

The Brexiters say they’ll force the EU to cave in and drop the backstop by “threatening”’ no deal. But they know this is an empty threat because the EU’s ability to absorb the shock of no deal is far greater than ours. The EU stance will continue: first resolve the divorce items, then we can talk about the future relationship.

Plenty who advocate a second referendum or revoking article 50 have refused to tolerate any form of Brexit, blocking compromises and then dismissing the withdrawal agreement bill (WAB) out of hand. As a consequence, 160,000 Tory no-deal hardliners will decide our fate – a textbook case of purists insisting that the most desirable must block the tolerable.

Yet even Johnson is finally understanding the disastrous implications of a no deal. He now says that his “preference” is to leave with a deal. But he has not yet recognised that the WAB is the only viable option on any table.

The WAB is far from ideal. Yet because of concessions to demands made by Labour during cross-party talks it does provide the only feasible means of preventing no deal. There’s a draft statutory commitment to a customs union until the next general election, to workers’ rights, to environmental standards, and even provision for a binding vote on whether the deal should be put to a confirmatory public vote. I have profound reservations about a second referendum, but in order to break the deadlock and avoid the chaos of no deal I would consider compromising. The WAB is the only pathway to another referendum, and I simply do not understand why advocates of another public vote cannot see this reality.

So, regardless of whether your priority is to prevent no deal, to seek a deal-based Brexit or to secure a second referendum, the WAB is now the only game in town. All else is just unicorn-hunting and virtue-signalling. Labour’s leadership should therefore declare now that if the new prime minister were to table the WAB then Labour MPs would be whipped to support it.

Why help to dig the Tories out of this hole? Because we must put the country first. But there is also a political point: a general election before Brexit would be just as disastrous for Labour as for the Tories. It would be completely dominated by Brexit, and would therefore overwhelmingly benefit single-issue opportunists such as Farage, the Lib Dems and the nationalists.

Brexit is tipping us into a culture war. We must reclaim our politics from the snake-oil salesmen and re-centre it on the vital issues of justice, opportunity, security and prosperity. The withdrawal agreement bill is a lifeline that Labour should grasp with both hands.

• Stephen Kinnock is Labour MP for Aberavon and a member of the select committee on Exiting the European Union