The DUP has rejected the "meaningless assurances" from the EU over the Irish backstop and called on Prime Minister Theresa May to deliver real changes to the Brexit withdrawal agreement.
European Union chiefs published a letter on Monday confirming that Brussels does not want the backstop to remain in place permanently after the United Kingdom leaves the EU.
However, DUP deputy leader Nigel Dodds said his party was not reassured by the EU clarifications.
“Despite a letter of supposed reassurance from the European Union, there are 'no legally binding assurances' as the Prime Minister talked about in December," Mr Dodds said. "In fact, there is nothing new. Nothing has changed."
The North Belfast MP said the letters bolstered the parties concerns by confirming that everything the Attorney General said in his legal advice regarding the backstop still stands, there has been no change to the withdrawal agreement and that Northern Ireland would be subject to EU laws with no representation in Brussels.
Instead of meaningless letters, the Prime Minister should now ask for and deliver changes to the withdrawal agreement. DUP MP Nigel Dodds
Regarding the Prime Minister’s comment about “changes to everyday life in Northern Ireland that would put the future of our Union at risk” Mr Dodds said: “The Prime Minister must explain this comment. What exactly would the Government be changing?
"If this is nothing more than scaremongering, then the Prime Minister should cease from such foolish talk. Indeed, the Irish Prime Minister Leo Varadkar has said that the Republic of Ireland is not making preparations for a hard border even in the event of no deal being agreed.”
The current backstop would see Northern Ireland remain in the customs union to prevent a hard border in the island of Ireland.
The Prime Minister warned MPs, who will vote on the withdrawal agreement on Tuesday evening, of the "catastrophic harm" voting down her deal would have on public faith in their elected representatives.
Mrs May also said that, if the withdrawal agreement was voted down, MPs risk a no-deal Brexit or Brexit not occurring at all.
With no deal we would have: no implementation period, no security co-operation, no guarantees for UK citizens overseas, no certainty for businesses and workers here in Stoke and across the UK, and changes to everyday life in Northern Ireland that would put the future of our Union at risk. Theresa May
"The only ways to guarantee we do not leave without a deal are to abandon Brexit, betraying the vote of the British people, or to leave with a deal," she said.
"The only deal on the table is the one MPs will vote on tomorrow night. You can take no deal off the table by voting for that deal.
"If no deal is as bad as you believe it is, it will be the height of recklessness to do anything else."
The Prime Minister said she had listened to the concerns of MPs, including the DUP, who currently prop up the Conservative government.
She said the letter from the EU contained "valuable new clarifications and assurances to put before the House of Commons, including on getting our future relationship in place rapidly so the backstop should never need to be used".
She added: "We now have a commitment from the EU that work on our new relationship can begin as soon as possible after the signing of the Withdrawal Agreement in advance of March 29, and we have an explicit commitment that this new relationship does not need to replicate the backstop in any respect whatsoever."
Mrs May said the EU had agreed to a "fast track process" to agree a new trade deal with the UK after Brexit, and that this made it more likely the backstop will never have to be used.
A restored Stormont would also have a say on any new EU rules that are added to the backstop.
Answering questions from journalists, Mrs May said: "You talk about Parliament taking control. What I think is important is that we deliver on the result of the referendum.
"What I'm concerned about from what we have seen, as I've said in my speech, over the last few days is the real prospect that we could see a, sort of, stymie in Parliament, or Parliament operating, or people in Parliament trying to operate in a way, that frustrates Brexit.
"We have a duty to deliver Brexit and that's what I and the Government want to do, and it is what we are going to do.
"I want MPs to recognise that as well."