After two years of tortuous negotiations, Theresa May’s strategy for taking the UK out of the EU lies in ruins. From the moment the stentorian attorney-general, Geoffrey Cox, pronounced that late legal changes won by the prime minister did not remove the risk of the UK being “trapped” in the so-called Irish backstop hated by Eurosceptics, her withdrawal agreement was headed for another crushing Commons defeat. The priority now must be to avoid chaos — chaos in parliament that could be exploited by extremists of left and right, and the chaos of a no-deal exit. MPs must stabilise the political situation and create the space for a Brexit rethink.

In other circumstances, a second humiliating loss on the government’s flagship policy would end in a prime ministerial resignation. Mrs May must bear most of the blame for the failure to secure a parliamentary majority. Her negotiating strategy was muddled and contradictory, and she continually put narrow party interests ahead of those of the nation. This premier, who prides herself on being no “quitter”, seems determined to try to soldier on. If she succeeds, against all odds, she must pursue a new strategy.

This means ending the fantasy of bringing her deal to parliament a third time. EU officials have made clear there will be no further concessions on the backstop aimed at avoiding a hard border in Ireland. Mrs May should instead allow parliament to take control. She must work to promote and facilitate exactly the kind of cross-party co-operation in the national interest that she has so far stubbornly resisted.

As a first step, MPs must vote on Wednesday to remove the risk of a catastrophic no-deal departure from the EU on March 29. Such an exit would do huge damage to UK jobs, prosperity and security. Bringing supply lines to a standstill, it could lead to shortages of foodstuffs and even medicines. It would destroy international trust in Britain when it most needs to forge new relationships.

There should be no prevarication here. Letting Britain crash out of the EU — as the Brexit ultras advocate — is not fulfilling the result of the 2016 referendum. This is not what most Leave voters thought they were backing. Failure to remove this risk would be a dereliction of parliamentarians’ duty to exercise their judgment in the best interests of the citizens they represent.

Join the Europe Talks project The Financial Times is collaborating with 16 news organisations for an experiment called Europe Talks, where we connect thousands of Europeans for face-to-face conversations across borders. Would you like to be involved? Click here to find out more.

MPs’ second priority is to vote on Thursday to seek from the EU an extension of the Article 50 withdrawal process. This needs to be longer than three months. It should allow time for a new approach to Brexit that tests MPs’ appetite for other forms of withdrawal. Indicative votes should be held on “softer” options including a permanent customs union with the EU — which this newspaper has supported — or a “Norway-plus” option of remaining in the single market and a customs union.

If no option can garner the support of a majority of MPs, the Financial Times has advocated returning the issue to the British people in another referendum. Voters could be presented with a choice between Mrs May’s deal — the only negotiated Brexit option that currently exists — or remaining in the EU. MPs might favour a general election. But with Britain’s two biggest political parties both riven over Brexit, an election would resolve little.

A new referendum would be divisive, but it would offer voters this time a real choice, instead of the illusory Brexit they were sold in 2016. A majority does not yet appear to exist in parliament for this route, either. Yet if MPs cannot unite around an alternative Brexit, they might start to see a new plebiscite as the only way out of the impasse.