The UK will not accept a Brexit deal that involves being indefinitely locked into a customs union with the EU, Dominic Raab has said.

The Brexit Secretary said that a provision on a customs union which was not “finite” would fail to deliver the result of the 2016 referendum.

Downing Street has insisted that Theresa May would never agree a Brexit deal with the EU which “traps” the UK permanently in a customs union.

The pledge came amid speculation over possible ministerial resignations if the Prime Minister gives too much ground ahead of a crunch Brussels summit next week.

European Commissioner Guenther Oettinger said on Friday that “it does appear possible there will be a breakthrough” at the October 17-18 summit, fuelling speculation a deal is near on a so-called “backstop” for the Irish border.

It is understood that a number of ministers voiced concern at a meeting with the PM in Downing Street on Thursday that any such backstop could leave the UK in an open-ended customs union, preventing it from seeking trade deals elsewhere in the world.

Mr Raab said: “It would have to be finite, it would have to be short and it would have to be, I think, time-limited in order for it to be supported here.

“What we cannot do is see the UK locked in via the backdoor to a customs union arrangement which would leave us in an indefinite limbo. That would not be leaving the EU.”

Cabinet meeting
Chancellor Philip Hammond suggested a backstop on the Irish border will ‘probably’ have to come into effect for a period (Jonathan Brady/PA)

Chancellor Philip Hammond became the first senior Government figure to suggest that the backstop – designed to keep the border between Northern Ireland and the Republic open in the case that no broader EU/UK trade deal is finalised – will “probably” have to come into effect for a period.

Nigel Dodds, deputy leader of the Democratic Unionist Party which props up Mrs May’s minority Conservative administration in the House of Commons, said he expected developments over the weekend “in terms of the Government’s own position and the Cabinet”.

The DUP is adamant it will not agree to anything which results in imposition of extra customs or regulatory checks between Northern Ireland and the rest of the UK.

Mrs May set out in June proposals for a “temporary customs arrangement” to ensure that the border between Northern Ireland and the Republic remains open in the case that no broader EU/UK trade agreement has been finalised.

The document stated that the UK Government “expects” this arrangement to remain in place no later than the end of December 2021.

However, the EU is mounting resistance to any specific time limit being included in the text of the UK’s Withdrawal Agreement while Leave-backing ministers are understood to be insistent that the end of the arrangement should be more precisely defined than the vague term “temporary”.

Irish Foreign Minister Simon Coveney insisted the backstop should be able to remain in place “unless and until something better comes along” and told ITV News it was a “deal breaker”.

As officials continued to wrangle over the precise wording of the agreement in Brussels, a Downing Street spokeswoman said the Prime Minister would “never agree to a deal which would trap the UK in a backstop permanently” and “our position is that this future economic relationship needs to be in place by the end of December 2021 at the latest”.

Leading Conservative Brexiteer Steve Baker said that any backstop which went beyond a simple free trade agreement amounted to “effectively committing the UK to membership of the single market and customs union”.

Mr Baker said: “That won’t wash. The British people voted to take back control over money, laws borders and trade.”

Downing Street has always been clear that it does not wish or expect the backstop option to be implemented, as it insists it will be possible to agree a wider trade deal guaranteeing an open border in Ireland by the end of the transition period in December 2020.

However, Mr Hammond told Bloomberg TV: “We are not going to remain in anything indefinitely, we are very clear this has to be a temporary period.

“But it is true that there needs to be a period, probably following the transition period that we have negotiated, before we enter into our long-term partnership, just because of the time it will take to implement the systems required.”

Following Thursday’s meeting of the “inner Cabinet” in Downing Street, Government Chief Whip Julian Smith insisted ministers were united behind the PM’s strategy.

Brexit
Works and Pensions Secretary Esther McVey has refused to endorse Theresa’s May’s Chequers plan (David Mirzoeff/PA)

However, Westminster was rife with speculation of possible resignations by hardline Brexiteers within the Government.

Earlier, Work and Pensions Secretary Esther McVey, who was not at the Downing Street meeting, pointedly refused to endorse the Prime Minister’s Chequers blueprint for Brexit.

International Development Secretary Penny Mordaunt and Leader of the Commons Andrea Leadsom – who, like Ms McVey, both backed Leave in the referendum in 2016 – were also said to harbour deep concerns.

As talks with Brussels continued, Whitehall published a series of documents on preparations for a no-deal Brexit.

They indicated the collapse of negotiations could threaten electricity blackouts in Northern Ireland, disrupt Channel Tunnel rail services and cost the UK free trade agreements with more than 70 non-EU countries around the world.