DUP leader Arlene Foster has said that Prime Minister Theresa May's Brexit plan could cause Northern Ireland to separate from the rest of the United Kingdom over the next decade.
In an interview with RTE Mrs Foster confirmed that her party would not support any Brexit withdrawal deal which includes a Northern Ireland only 'backstop' and a border in the Irish Sea.
It was revealed on Thursday that a letter sent to Mrs Foster and deputy DUP leader Nigel Dodds suggested that the Prime Minister would be willing to include a Northern Ireland specific 'backstop to the backstop' in the final Brexit withdrawal deal.
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
The backstop would see Northern Ireland remain in the EU single market and customs union in the absence of a trade deal being agreed between the UK and EU.
It is intended to avoid a hard border on the island of Ireland and the EU's Chief Brexit Negotiator Michel Barnier and Taoiseach Leo Varadkar have insisted it must be part of any UK withdrawal agreement.
Prime Minister Theresa May has countered the plan by suggesting that the entire UK could remain inside the customs union for a time limited period.
However the EU have said that that any backstop could not be time limited, and must remain in place until Brexit issues regarding the future relationship between the UK and the EU are fully resolved.
A 'backstop to the backstop' would involve only Northern Ireland remaining tied to the EU in the event that a trade agreement could not be reached within the time limited period.
The DUP claim the plan would effectively separate Northern Ireland from the rest of the UK and create a border in the Irish Sea.
Mrs Foster said that the DUP would not be able to support the Prime Minister's plan in Parliament.
Mrs May currently relies on the support of ten DUP MPs to get key legislation, including Brexit, through Parliament as part of their confidence and supply agreement.
DUP leader Foster suggested that her party's position had support from senior Conservative Party figures saying that Mrs May had "a job of work to do to get this through cabinet".
Mrs Foster said the plans would cause a "democratic deficit" giving the EU power over Northern Ireland, without Northern Ireland having a say and could lead to Northern Ireland "diverging away" from the UK over the next decade.
She told RTE that her party only had "one red line" and that they were determined to protect the union.
The DUP leader suggested that if Mrs May wanted to pursue the current proposals she could so without the support of the DUP's ten MPs.