Leader: The question for Theresa May is now whether Brexit is deliverable at all

Her Chequers plan commands neither the support of her party nor the European Union.

Brexit has never been deliverable under the terms that were promised. The question now is whether it is deliverable at all. Just months before a withdrawal deal needs to be approved, Theresa May’s Chequers plan commands neither the support of her party (as the Conservative conference will demonstrate) nor the European Union.

The EU’s smug and imperious dismissal of the Prime Minister’s proposals was no surprise. Since 2016, European leaders have warned Britain repeatedly that it cannot “cherry-pick”. It cannot be part of the single market for goods (as Mrs May proposes) but outside it for services.

To concede otherwise would undermine one of the EU’s cardinal principles, that the four freedoms – the free movement of goods, capital, services and labour – are indivisible. Were Britain granted an exception, it would be an invitation for others (Italy, say) to demand equivalent treatment.

It was Xavier Bettel, the prime minister of Luxembourg, who perhaps put it best in 2016: “Before, they were in and they had many opt-outs; now they want to be out with many opt-ins.” The Brexiteers are merely discovering what was clear all along: there is no cost-free option for the UK. And by triggering Article 50, Britain gifted the EU greater influence over its domestic affairs than ever before.

Although Mrs May’s Chequers plan is defunct, her Tory opponents have no viable alternative. Some, such as the former Brexit secretary David Davis, speak of a “Canada-style deal” but offer no solution to the Irish border problem. Others, such as Jacob Rees-Mogg, suggest leaving with no deal at all. But, as Mrs May knows, this would be an act of national self-harm for which Britain is unprepared.

Labour has its own divisions. At the party’s conference in Liverpool, the shadow chancellor, John McDonnell, and Unite’s general secretary, Len McCluskey, both suggested that any second referendum would be focused narrowly on whether to accept the government’s deal, rather than revisiting the idea of staying inside the EU.

However, in line with the motion later passed by activists, Mr McDonnell conceded that continued membership could not be ruled out. If parliament rejects any deal that Mrs May agrees, a general election should follow in which Labour outlines a coherent alternative. As some have suggested, this could involve a Norway-style deal – membership of the European Economic Area – subject to a referendum.

Yet even a new election, which could result in another hung parliament, may not resolve the impasse. For a country of Britain’s size and status, this is a humiliating situation. Mrs May has undoubtedly made errors along the way, but it would be wrong to blame only her for this state of affairs. The problem lies not just in the handling of the Brexit negotiations, but with Brexit itself. For this, David Cameron bears the most responsibility. It was the former prime minister who put party before country by holding the 2016 referendum and imposed the punitive austerity that helped create the conditions for the Leave vote. After repeatedly bemoaning the “mess created by Labour”, Mr Cameron left one of his own – and we will all suffer because of it.