Alliance Brexit spokesperson Stephen Farry MLA has said while aspects of the proposed backstop could be applied UK-wide, at its core it must remain open-ended.
Dr Farry was responding to the Prime Minister's statement to the House of Commons on the EU Council Summit last week.
He said: "Alliance's preference continues to be a People's Vote to reconsider Brexit or a soft Brexit UK-wide. The backstop is only our insurance to protect the Good Friday Agreement and to ensure an open border in Ireland.
"At a minimum, Northern Ireland does need to follow the relevant rules of the single market and be part of the same customs area. We have no objection and indeed would welcome elements of the backstop being UK-wide. However, the backstop is not a backstop unless it is open-ended until and unless a better solution is found. That is the critical point.
"The continued focus on time-limits is at odds with the intent of the backstop and what has already been agreed by the UK Government in the December 2017 Joint Report and commitments already made around the Withdrawal Agreement.
"The Prime Minister is running out of time and has already missed the deadline for a negotiated withdrawal from the EU. She needs to accept and take forward what has already been agreed. To do otherwise risks a no-deal outcome and jeopardises the UK economy and the cohesion of society."