The DUP's Sammy Wilson has warned his party will not support a floated deal which could see a 'backstop to the backstop' used to facilitate the UK's exit from the European Union. (Brian Lawless/PA)

The DUP's Sammy Wilson has warned his party will not support a any deal which could see the backstop insurance policy - which would keep NI aligned with the EU on customs arrangements - used to facilitate the UK's exit from the European Union.

The proposal emerged in a letter from Prime Minister Theresa May to DUP leader Arlene Foster and leaked to The Times.

Speaking on Friday, East Antrim MP Mr Wilson said: "There is a large number of issues which have been raised in this letter which raise alarm."

In the letter the Prime Minister says the EU wants a provision in which Northern Ireland remains in the customs union if no other post-Brexit arrangement is reached.

1/2 1st November 2018 letter from Arlene Foster @DUPleader & Nigel @NigelDoddsDUP to the Prime Minister. "Unlike the previous political declarations, the scope for delay, fudge or obscurantist language has passed. This is now a time for clarity and plain speaking." pic.twitter.com/QSSm3eM3Pw — DUP (@duponline) November 9, 2018

In her response, Mrs May states she would not accept a situation where the backstop "could come in to force" - phrasing the DUP has taken exception to.

Speaking to Radio Ulster's Good Morning Ulster programme, Sammy Wilson said "the insurance policy argument" was a "false one" and warned his party would vote down the deal proposed in the letter if it was put before the House of Commons.

Mr Wilson said his party was "hoping to turn the Prime Minister around".

"We want to stick to the confidence-and-supply arrangement, but you know there are two sides to that. The government has obligations under the confidence-and-supply arrangement and as have we," he said.

"We are seeing the shape of the agreement she is talking about in this letter. We don’t like the shape of it. We are warning the Prime Minister again it breaches the promises she made, time and time again in the House of Commons and when she visited Northern Ireland.

"We are asking her to reconsider this. We are asking members of her cabinet to reconsider this."

"The EU has made it clear that as far as they are concerned there is no solution to the problem which they envisage at the Irish border other than the backstop arrangement. The fact that they have turned down I don’t know how many proposals from the UK Government is a fair indication they want this insurance policy put in place at one place."

The leaked letter also suggests that the whole of the UK could remain closely tied to EU, as the UK Government does "not expect regulations to diverge between Great Britain and Northern Ireland".

Mrs May wrote that the backstop was "an insurance policy that no-one in the UK or the EU wants or expects to use" and that it would not last indefinitely.

The five-page letter was sent in response to an earlier correspondence from the DUP, in which Mrs Foster and the party's leader in the House of Commons Nigel Dodds outlined their expectations for the post-Brexit agreement.

Belfast Telegraph