Brexiteers often hark back to the blitz. Maybe they think the “Britain standing alone” motif adds much-needed heroic purpose to a Brexit future in which Britain stands without trading partners or allies to tackle climate change.

But they rarely invoke one feature of wartime: the national government steering Britain from disaster. Now that Britain faces its gravest emergency since the war, we might soon need another national government, purely to deliver a Brexit referendum.

The crisis demands a backbench rebellion with the likes of Yvette Cooper and Hilary Benn working with the reinvigorated Liberal Democrats to bring down this rotten government. Jeremy Corbyn calls constantly for a general election but no Tory MP will pass a vote of no confidence in the government if a general election will follow. But might the likes of Dominic Grieve and Oliver Letwin join with progressive MPs to vote down a government committed to no deal if no election came next? Even Philip Hammond would.

First, this backbench coalition must come together to prevent an incoming Tory leader proroguing parliament and forcing a no-deal Brexit on an increasingly doubtful public. If Boris Johnson tried that, it would be an effective putsch or coup d’etat against parliament. MPs who vote to stop such a hard Brexit no-deal coup would, in effect, self-select as supporters of a national government.

This is no attempt to gain power through coalition. Such a government of national unity would be short-lived and have one policy: to deliver a referendum. Even if more policy agreement could be found, there would be no point: as Theresa May has demonstrated, government currently lacks bandwidth to deliver Brexit, let alone more.

If Boris Johnson tried forcing a no-deal Brexit on an increasingly doubtful public, it would be an effective coup d'etat

After a referendum, there would soon have to be a general election. Other MPs could return to their parties, and as Liberal Democrat leader I would take my party back into opposition and fight to win that election. But in parliament today we should recognise that Brexit has broken the party system. And just as one party proved incapable of delivering Brexit, so we will need more than one party to stop Brexit.

Meanwhile, we need pro-European Labour figures who voted LibDem in their thousands to join us to give this move momentum (in the genuine sense of the word). I disagreed profoundly with Alastair Campbell and co over Iraq, but on the great issue of today we are on the same side against hard-right, dangerous nationalism.

Any genuine progressive should work together to stop Brexit – this is a national emergency, requiring national cooperation.

• Ed Davey is the MP for Kingston and Surbiton