Theresa May could have to choose between the DUP and Tory Brexiteers

Irritation from Conservative Leavers over the prime minister's pledges on the Irish border means she might have to jettison them to keep the unionists on side. 

NS

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In the not-so-distant past, the three letters that worried Theresa May most on Brexit weren’t ERG but DUP. But in the very public spat over the Chequers plan, its MPs – who keep the government in power – have been largely inconspicuous. 

At past crunch points on Brexit, they have made the prime minister’s life very difficult indeed. So what’s different this time? 

The simple answer is that the plan does not contravene their most important red line opposition to a new border in the Irish Sea, or any differential arrangements within the UK’s internal market. This is the same as it ever was, and won’t change.

Nigel Dodds, the DUP’s leader at Westminster, and Sammy Wilson, the party’s Brexit spokesman and the most ideological Eurosceptic of its 10 MPs, both gave a qualified welcome to the Chequers plan on the grounds that it satisfies that demand. 

That both of them did underlines the fact that, ultimately, no aspect of Brexit matters more. So too does the fact that of the four wrecking amendments to the trade bill tabled by Jacob Rees-Mogg and the ERG today, the DUP only put its name to one – a proposal that would make any deal that treated Northern Ireland as part of the EU’s customs territory illegal. 

I understand there are still some lingering concerns over whether the deal would give Brexit Britain freedom to strike new trade deals, but should these be assuaged by the government’s White Paper – and the survival of Liam Fox as international trade secretary suggests they will – then May will be out of the woods.

For now, that is. The prime minister’s problem is that more and more Conservative MPs are expressing frustration with the fact that the backstop agreement to maintain an open Irish border is essentially blocking the swashbuckling Brexit they want. 

Both Ben Bradley and Maria Caulfield, the Tory vice chairs who resigned yesterday, made pointed complaints to that effect: Caulfield said it was "neither necessary or constructive", and Bradley complained that it had been allowed to become "the deciding factor for the whole of the UK's economy and trade policies”.

These complaints highlight the fact that beyond the DUP, few Brexiteers actually understand the government’s pledge to maintain the constitutional integrity of the union. Fewer still, it seems, actually care. 

Therein lies the challenge for May: her promises on not installing a border on land or down the Irish Sea can only be fulfilled by pursuing a relatively soft Brexit for the whole UK. But while the DUP are likely might take it as a least worst option on the grounds that it satisfies their most important demand, Tory Brexiteers won’t swallow it on the grounds that it isn’t a real Brexit. 

Soon, she is going to have to choose which group to jettison. 

Patrick Maguire is the New Statesman's political correspondent.