Theresa May has said that her backstop plan to keep Britain aligned to the customs union beyond 2020 would only apply in a “very limited” set of circumstances as Brexiters ratcheted up pressure on her over the future customs relationship.

The prime minister said nobody wanted the UK to resort to the option despite persuading her “war cabinet” to sign up to new proposals last week, marking rare progress on Brexit after weeks of deadlock.



Her remarks come after Boris Johnson issued a thinly veiled warning that he and his fellow Brexiters would still expect May to deliver a deal on customs that avoided triggering the backstop, one of the sticking points in talks with Brussels.

The foreign secretary said that leave supporters who feared betrayal over future customs arrangements should understand that the prime minister was “very clear that this is not an outcome we desire”.

The environment secretary, Michael Gove, told an event organised by the Policy Exchange thinktank: “The whole point about the backstop is that it’s intended not to be implemented, but it’s there just in case.”

May rejected the EU’s version of the backstop, which would involve keeping Northern Ireland in the customs union to avoid a hard border, in February when she told parliament no prime minister would accept the UK being so divided.

However, some in Westminster believe that if Brussels accepts the UK’s alternative plan, which would retain key aspects of the customs union if a solution to the Irish border problem has not been found, it could become the post-Brexit norm.

In a speech in Macclesfield on Monday, May said: “What we’re proposing is an alternative backstop proposal, but nobody wants this to be the solution that is achieved.



“We want to achieve the right solution through our overall relationship with the European Union. If it is necessary, it will be in a very limited set of circumstances for a limited time. But we are working on achieving that commitment to Northern Ireland through our overall relationship with the European Union.”

The cabinet remains deadlocked over the final customs arrangement Britain that should pursue and HMRC officials believe neither model under consideration will be ready to implement the end of the transition period in December 2020.

It remains unclear whether the EU27 will accept the government’s version of the backstop plan, which would see the UK continue to apply EU tariffs to imports but leave it free to strike new trade deals.

Meanwhile the prime minister and Jeremy Corbyn will be in Manchester on Tuesday on the first anniversary of the Manchester Arena bombing.

Writing in the Manchester Evening News, the prime minister said: “The targeting of the young and innocent as they enjoyed a carefree night out in the Manchester Arena on May 22nd 2017 was an act of sickening cowardice.

“It was designed to strike at the heart of our values and our way of life in one of our most vibrant cities with the aim of breaking our resolve and dividing us.

“It failed, for such appalling acts of wickedness will do nothing but strengthen our resolve to defeat such twisted ideologies and beliefs.

The resilience and determination shown by Manchester in the 12 months since is testament to that.”