British Prime Minister Theresa May will 'betray' Ireland and her own Brexit deal with the European Union after ordering MPs to vote for an alternative to the backstop.
There was dismay in Dublin last night as it emerged Mrs May told her party to back a House of Commons vote which seeks to replace the backstop with "alternative arrangements".
One senior Government source described the development as "May's betrayal", while another said it would send "shockwaves" through Europe.
The shift in policy by the British government has moved the prospect of a no-deal scenario even closer.
Mrs May has consistently defended the backstop as the only definitive way to avoid a hard Border, even previously stating: "There is no deal available that does not include the backstop."
However, with exactly two months until Brexit, she has now urged her party to get behind a motion that seeks to have it replaced with an undefined alternative.
The backstop is an 'insurance policy' which ties the UK to European regulations in order to prevent a hard Border in Ireland.
It will stay in place "unless and until" a better solution is agreed - but many UK politicians fear being trapped in the EU customs union and single market indefinitely.
Ireland and the EU have repeatedly insisted they want a new deal in place by the end of a transition period in 2020, meaning the backstop would never actually be activated.
Irish sources said if the amendment being proposed tonight by Conservative MP Graham Brady is passed it will severely heighten the risk of a no-deal Brexit.
Referring to Mrs May's flip-flop on a deal which she negotiated, a source said: "The feeling here is disappointment in an act of bad faith."
Although Mr Brady has not specified that he wants the Withdrawal Agreement between the UK and EU reopened, it is likely any change to the backstop would require this. The EU has categorically ruled out a renegotiation of the deal ahead of March 29.
Mr Brady said his amendment would give "enormous firepower" to Mrs May when she returns to Brussels.
Tánaiste Simon Coveney said yesterday the EU will not ratify any Brexit treaty unless it includes the backstop.
"We have made it very clear that the time for debate and discussion over the backstop was when it was being negotiated," Mr Coveney said.
"People refer to it as the Irish backstop... the backstop was a series of compromises agreed with the British government, with the EU negotiating teams and signed off by all 28 governments including the British government at the end of two years of negotiation."
The EU's deputy chief negotiator Sabine Weyand said there was "full ownership of what was agreed" in the EU, but "no ownership" of it in the UK Parliament.
Even if Mrs May orders her MPs to back the Brady Amendment, there is no certainty that it will command a majority in the House of Commons.
Hardline Brexiteer Jacob Rees-Mogg told reporters he feared it does not go far enough. It has also now emerged that some Brexiteers and Remainers have thrashed out an "olive branch" solution which was presented to Number 10 last week, involving an extension of the 21-month transition period with a reworded backstop clause. This is now seen as 'Plan C'.