Brexiters who reject Theresa May’s deal will drive the UK towards a permanent customs union with the EU, Downing Street has warned as the government tries to forestall a rash of resignations before next week’s historic vote.

The prime minister will spend the weekend at her country retreat of Chequers before embarking on what some at Westminster believe could be the closing act of her premiership.

With the parliamentary arithmetic looking bleak for the prospects of the deal being passed, she has been warned personally by several Brexit-backing government aides that they are prepared to resign on Tuesday unless there are major changes to her deal. Leavers are concerned the UK could be trapped indefinitely in the Irish backstop.

Quick guide Brexit and backstops: an explainer Show Hide A backstop is required to ensure there is no hard border in Ireland if a comprehensive free trade deal cannot be signed before the end of 2020. Theresa May has proposed to the EU that the whole of the UK would remain in the customs union after Brexit, but Brussels has said it needs more time to evaluate the proposal. As a result, the EU insists on having its own backstop - the backstop to the backstop - which would mean Northern Ireland would remain in the single market and customs union in the absence of a free trade deal, prompting fierce objections from Conservative hard Brexiters and the DUP, which props up her government. That prompted May to propose a country-wide alternative in which the whole of the UK would remain in parts of the customs union after Brexit. “The EU still requires a ‘backstop to the backstop’ – effectively an insurance policy for the insurance policy. And they want this to be the Northern Ireland-only solution that they had previously proposed,” May told MPs. Raising the stakes, the prime minister said the EU’s insistence amounted to a threat to the constitution of the UK: “We have been clear that we cannot agree to anything that threatens the integrity of our United Kingdom,” she added.

Mike Wood, the parliamentary private secretary to the trade secretary, Liam Fox, told the Guardian he would quit his post and join leave-supporting backbenchers unless changes were made to the backstop. It is understood that other junior ministers have made similar representations and more were considering their positions.

The Telegraph reported that some cabinet members had warned May she would have to stand down if the deal was defeated and she failed to secure better terms from Brussels. The Times said Labour was hoping to persuade some Tory rebels and the DUP to join forces with it to unseat her.

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Restive pro-leave MPs have been warned, however, that if May’s deal fails they will end up with a softer Brexit based on a judgment by No 10 that there is a parliamentary majority for a customs union.

MPs passed an amendment earlier this week which ensures that, if May’s deal was voted down, any motion setting out next steps will have to be amendable.

Supporters of alternatives, including Labour’s “comprehensive customs union” and a second referendum, are expected to use the opportunity to test support for their preferred option.

Government sources said: “The greater the role for parliament, the softer that [deal] gets. If you’re not a supporter of a customs union, you need to vote for this deal.”

May’s spokesman insisted on Friday that the Brexit vote would go ahead on Tuesday, despite growing pressure to delay it, including from some cabinet ministers, and the chair of the 1922 Committee of backbench Conservative MPs, Graham Brady.

Wood, the MP for Dudley South, was one of more than a dozen elected ministerial aides who met the prime minister last week to express their concerns about the EU withdrawal deal.

The chief whip, Julian Smith, is relying on the “payroll vote” of more than 100 MPs with government positions to support May in the hope of containing the majority against the prime minister’s deal.

Wood said on Friday he had told May he would have to resign unless there were significant changes to the backstop.

He said: “What I have indicated to the prime minister is that, while I support most of the deal, I have some big issues with the backstop. If some of those aren’t addressed then I don’t think I will be able to support it.

“Clearly the ministerial code says that if I can’t support, I would have to resign. I am very much hoping that there are enough changes and reassurances by Tuesday for me to vote with the government.”

Wood, whose constituency voted 71% to leave, said he had met May with two backbenchers who also expressed concerns about the backstop.

“The prime minister has had lots of meetings with lots of colleagues with a lot of different views to hear feedback,” he said. “I want some mechanism to be in place so that we either don’t go into the backstop provisions, or if we go into it we have a clear way of getting out again. This could be achieved in a number of different ways so I will obviously look at the proposals as they are on Tuesday before I decide whether to go.”

Wood said many other junior ministers would be considering their options over the weekend. “A clear majority [of parliamentary private secretaries] will vote with the government on Tuesday. There are others who have a range of questions and concerns that they will want to be resolved before making their decision,” he said.

The Labour MP Virendra Sharma, who supports the anti-Brexit campaign group Best for Britain, said: “Even a member of Liam Fox’s team doesn’t believe his boss’s protestations that this is a good deal. You can see a slow motion car crash happening in front of our eyes. It looks like the fox has been well and truly shot.”

Wood’s fellow Dudley MP, Ian Austin, who represents the north of the town, is one of the few Labour MPs to have suggested May’s deal meets his party’s six tests.

Quick guide What are Labour's six Brexit tests? Show Hide Does it ensure a strong and collaborative future relationship with the EU?

Does it deliver the “exact same benefits” as we currently have as members of the single market and customs union?

Does it ensure the fair management of migration in the interests of the economy and communities?

Does it defend rights and protections and prevent a race to the bottom?

Does it protect national security and our capacity to tackle cross-border crime?

Does it deliver for all regions and nations of the UK?



The prime minister dispatched more than 30 of her ministers around the country on Friday in what Whitehall sources called a “starburst” to sell the deal to the public.

The prime minister signalled on Thursday that MPs would be given a vote in 2020, when the UK would have to decide between entering the backstop, or extending the transition period, if no permanent agreement had been reached that avoids the need for a hard border.

Backbenchers tabled an amendment on Thursday night, thought to have the tacit support of the government, pledging a vote in those circumstances and obliging the government to seek fresh reassurances from the EU27 that the backstop is not intended to last more than a year.

The Democratic Unionist party, which has effectively withdrawn its support from May’s government in protest against the backstop, rejected the amendment.

Meanwhile, Ireland’s European commissioner has hit out at a suggestion from the Tory MP Priti Patel that the UK government could use the threat of food shortages in Ireland as a result of no deal to win concessions on the backstop.

Phil Hogan, the commissioner for agriculture, said any block on Irish exports to Britain would lead to “the starvation of the British people”, not the Irish, because 43% of food consumed by the UK came from Ireland.

Patel’s remarks were widely condemned as insensitive, given Britain’s role in the Irish famine in the 1840s, and ignorant of Britain’s poor food security.

Hogan said consumers would be “horrified” that a senior politician would be so “hostile to the food security requirements” of the country where she lived.

• This article was amended on 10 December 2018 to correct the decade given for the Irish famine or Gorta Mór (Great Hunger).