Alliance Brexit spokesperson Stephen Farry MLA has expressed sadness at the conclusion of the UK-EU Withdrawal Agreement, saying it is not a moment for celebration.
Dr Farry added the backstop must be the "bare minimum" for the way forward, and cannot be "diluted or negotiated downwards".
He was speaking after EU leaders approved the agreement on the UK's withdrawal.
"There is no such thing as a good or sensible Brexit. The EU has been central to economic opportunities for the UK as whole, and for reinforcing peace and progress across Europe and here in Northern Ireland. Therefore the conclusion of the Withdrawal Agreement is not a moment of celebration but profound sadness," he said.
"However, in the context of Brexit, this Withdrawal Agreement represents the best deal the UK is going to get. For Alliance, the backstop itself is absolutely vital to protect the Good Friday Agreement and to avoid a hard border.
"The notion of the negotiations being reopened to ditch the backstop is delusional. The backstop is intrinsic to any Withdrawal Agreement. Moreover, the time to renegotiate before next March doesn't exist.
"At the very least, the backstop now needs to be banked. The economic and constitutional arguments being deployed against it are entirely spurious. The future for this deal remains uncertain. A no deal situation must be avoided at all costs.
"However, given all that has happened and what we now know, any opportunity to pursue a softer, EEA-style Brexit or to have a referendum should be taken. It is Alliance's preference Parliament puts this deal to a People's Vote."