Northern Ireland's four pro-Remain parties have issued a joint statement urging the EU to stay firm on its position on the Irish backstop.
Sinn Fein, the SDLP, Alliance and the Green Party said they believe the backstop contained in Theresa May's Withdrawal Agreement is a "vital insurance policy" to prevent a hard border on the island of Ireland.
The backstop is a mechanism that would see Northern Ireland remain in the EU customs union and large parts of the single market, preventing the need for any border checks or infrastructure if a more suitable arrangement cannot be found by Brexit day.
Earlier this week, MPs in the Commons passed an amendment that called for the Irish backstop to be replaced with "alternative arrangements to avoid a hard border".
Some of the "alternative arrangements" mooted by Prime Minister Theresa May include technological solutions or a "trusted trader" scheme.
Theresa May will now go back to Brussels to try and negotiate changes to the backstop, however the EU's chief negotiator Michel Barnier said this week the mechanism is "part and parcel" of the UK's Brexit deal and will not be renegotiated.
In a statement on Thursday, Northern Ireland's four pro-Remain parties said that while the current Withdrawl Agreement is imperfect, it will mitigate against a "bad Brexit".
"While it may never need to be deployed, the backstop is the guarantee in all circumstances that no hard border will be re-established on this island," they added.
"Prime Minister Theresa May and her government in their attempts to abandon the ‘backstop’ have demonstrated an enormous act of bad faith.
"Abandoning the backstop would put at real risk the interests, rights and entitlements of the citizens, households, businesses and the Good Friday Agreement endorsed overwhelmingly in 1998.
"While Westminster has voted this week against a No Deal Brexit, it is non-legally binding, and therefore no steps have yet been taken to prevent a catastrophic crash out from the EU on 29 March."
The parties said the EU has been "crystal clear" in stating they will not reopen negotiations on the Withdrawal Agreement and said any opportunity to reconsider Brexit should be taken.
"We urge the EU to remain firm in that position and call on the British Government to reconsider the reckless path that they have adopted," they added.