Downing Street says prime minister will not agree Brexit deal which traps UK 'permanently in customs union'

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

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.

After Mrs May briefed key ministers on the latest developments in the Brexit negotiations in Downing Street on Thursday evening, attention at Westminster is focusing on the issue of whether a precise time limit can be set on her proposed “backstop” arrangement for the Irish border.

Mrs May chaired a meeting of the inner Cabinet on Brexit progress Credit: Andrew Matthews/PA

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.

But the EU is mounting resistance to any specific time limit being included in the text of the UK’s Withdrawal Agreement.

Meanwhile, a Cabinet source told ITV News that Leave-voting politicians want to see "exact language on a 'temporary' backstop" before they give the prime minister their backing.

Brexiteers, the source said, want a legal guarantee the backstop can be terminated at Britain's will.

The Irish Foreign Minister Simon Coveney told ITV News an open-ended backstop is a "deal-breaker" adding that he does not believe that a Brexit deal can be done by next week's EU summit.

While the UK remains in a customs union with the EU, it cannot strike free trade deals with other countries like the US or China.

Brexiteers fear that once Britain is signed up to any sort of “temporary” arrangement, the EU will seek to drag it out into the indefinite future.

As officials continued to wrangle over the precise wording of the agreement in Brussels, a Downing Street spokeswoman told a Westminster media briefing: “The Prime Minister would never agree to a deal which would trap the UK in a backstop permanently.”

The spokeswoman said Mrs May stood by her June proposals, adding: “Our position is that this future economic relationship needs to be in place by the end of December 2021 at the latest.”

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.

But Chancellor Philip Hammond has now suggested that he believes the backstop will “probably” be needed for a period.

He 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.

“It’s very important to us that business doesn’t have to make two sets of changes, that there will be effectively continuity from the current set-up through the transition period into any temporary period and then a single set of changes when we move into our long-term new economic partnership with the European Union.”

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

Works and Pensions Secretary Esther McVey has refused to endorse Theresa’s May’s Chequers plan Credit: 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 the 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.

A number of ministers, including Foreign Secretary Jeremy Hunt, Brexit Secretary Dominic Raab, Environment Secretary Michael Gove and International Trade Secretary Liam Fox, were said to have raised concerns over the backstop issue during the 90-minute meeting.