Arlene Foster has accused the Government of having a "chaotic" approach to Brexit as she warned the Prime Minister that verbal promises aren't enough and the backstop must be binned.
The DUP leader was speaking as Theresa May called off a vote on the Withdrawal Agreement in Parliament so she can return to Brussels and attempt to secure concessions. But Taoiseach Leo Varadkar last night warned against re-opening negotiations around the backstop.
The Prime Minister had faced defeat by a wide margin with Tory rebels set to join the DUP, Labour and the opposition parties in voting down her deal.
Mrs Foster said the deferral of the vote summed up "the chaotic nature" of the Government's approach.
"The Prime Minster was warned that this deal would not work but did not listen. The fundamentally flawed Withdrawal Agreement would have undermined our UK economy and the Union itself," she said.
"The backstop would have left Northern Ireland trapped as a hostage to the EU. The Prime Minister must get rid of the backstop. It is not needed. No one is building a 'hard border' between Northern Ireland and the Republic of Ireland."
The DUP leader said her "message was clear" in a telephone conversation with Mrs May. "I was categorical that pledges, promises or piecemeal remedies will not work. Unless it is part of the legally binding international treaty, it will not fly with the DUP," she added.
But the Taoiseach said: "The Withdrawal Agreement, including the Irish backstop, is the only agreement on the table.
"It took over a year and a half to negotiate and has the support of 28 governments and it's not possible to reopen any aspect of that agreement without reopening all aspects of it.
"I have no difficulty with statements that clarify what is in the Withdrawal Agreement but no statement of clarification can contradict what is in the Withdrawal Agreement."
Sinn Fein president Mary Lou McDonald described Brexit as a shambles. "Theresa May and the British Parliament are deluding themselves if they think that Irish interests will simply be cast aside to facilitate the fantasy Brexit they are pursuing," she said. "The Irish Government and the EU need to stand by their commitments and defend Irish interests: there can be no hard border; no diminution of our rights; and protection for the Good Friday Agreement in all its parts."
SDLP leader Colum Eastwood said the Prime Minister may be able to change her mind multiple times on the backstop but the European Commission and the Irish Government can't and won't.
"Whether it is Theresa May, Jeremy Corbyn, Boris Johnston or any other future British Prime Minister, they need to come to terms with the fact that there will be no deal without a backstop," he warned.
Ulster Unionist leader Robin Swann said the Government had "driven itself into a cul-de-sac" and the backstop was an insurance policy NI did not need.
"Northern Ireland's position within the UK should not be the compromise sought for the sake of delivering a deal," he said.
"The Prime Minister should stand up and be uncompromising in her role as a defender of the economic and constitutional integrity of the United Kingdom."
TUV leader Jim Allister said: "Mrs May's humiliating climbdown highlights her folly in trying to push ahead with a deal that will never fly in Parliament.
"But, clearly, she has learned nothing because all she is now talking about is 'assurances', which will be meaningless in comparison to the legal text of the Withdrawal Agreement which she is not seeking to change."
The TUV leader accused Mrs May of "peddling nonsense" that the Good Friday Agreement required the backstop. "The Belfast Agreement does not require Northern Ireland to be in the EU Customs Union; the backstop does," he said.
"The Belfast Agreement does not require a border down the Irish Sea; the backstop does.
"The Belfast Agreement does not prohibit border infrastructure, but who would build this infrastructure, which is emotively called a 'hard border'? Dublin says it won't. The UK says it won't. So, why is she insisting on a destructive backstop on this false premise?"
Alliance leader Naomi Long stressed the need to "bank the backstop" and advised the Prime Minister to call a second referendum. Mrs Long said the delayed vote represented "further instability and challenges for jobs and growth" in Northern Ireland.
She accused MPs who opposed the Withdrawal Agreement of offering no alternative.
"It now looks increasingly likely that Brexit is undeliverable. Those who campaigned for it are entirely responsible for the failure. They had no plan and completely unrealistic expectations of the UK's negotiating strength against 27 other nations in the EU," she said.
"Instead of accepting the Withdrawal Agreement which would ensure an orderly, managed Brexit could proceed, they instead want to drag the country over a cliff edge into a chaotic future."