DUP Westminster leader Nigel Dodds has indicated that his party would bring Theresa May's government down if the Prime Minister got her Brexit deal through the House of Commons.
DUP support for Mrs May’s administration in any confidence motion would depend on the deal being defeated or ditched by the Prime Minister.
Mr Dodds told ITV's Peston the DUP would not be voting for Mrs May's Withdrawal Agreement "as things stand", adding he could not see "much being changed that will be effective" before the meaningful vote on December 11.
The Prime Minister's deal was "bad for the United Kingdom, certainly bad for Northern Ireland given the legal advice that we have forced out of the government today," Mr Dodds told Robert Peston.
"The deal that the Prime Minister has put forward is not one that honours the spirit of the confidence and supply agreement and certainly not one we can support," he said.
Earlier on Wednesday, Mr Dodds met with European Research Group (ERG) Chairman Jacob Rees-Mogg and Deputy Chairman Steve Baker and told the Brexit-backing Tories that the DUP's support for Mrs May could be conditional on the deal being defeated.
When questioned on it, Mr Dodds said it would be "somewhat illogical" if the DUP wanted to vote the Government out after forcing Mrs May's hand should the vote go against her on December 11.
"I think then we start on a process to try to get a better deal," he added.
He added opposition to the Withdrawal Agreement have been "galvanised" by the publication of the "devastating" legal advice.
When asked if he felt betrayed when the Attorney General report said Britain would be treated as a ‘third country’ for goods when it came to Northern Ireland, he said: “I think that that has really cut home to a lot of people. It is a devastating, I’d describe this as devastating, because it shows in terms that we’re in actually the EU customs union, GB treat Northern Ireland as a third country, we’re tied into it despite talk of it not being permanent, that it’s indefinitely and at the behest of the EU whether they ever let us out of it if we go into it. Yes, this is very, very wounding."
The Attorney General's Brexit legal advice was published in full on Wednesday following the Government's defeat in the House of Commons on Tuesday.
It warned the United Kingdom could be left in “protracted and repeated rounds of negotiations” over the Irish backstop.
In an attempt to win over MPs to vote in favour of the Withdrawal Agreement, Mrs May mooted the idea of a “Parliamentary lock” - giving MPs a vote before the backstop - could be implemented.
But Mr Dodds dismissed the idea that a "Parliamentary lock" could be offered by the Government, giving MPs a vote before the backstop is implemented.
"I don't see what that really accomplishes, it doesn't change anything, it doesn't change the withdrawal treaty, it doesn't have any effect on that whatsoever," he said.
He said it was "highly unlikely" that Mrs May would win the December 11 vote, but if the deal passed it would have "implications", warning the next steps would be even harder.
"But even before we get to the point of calling a general election, what I would say to the government and any Conservative MPs who may be thinking of voting for this - even if this vote squeaks through, how do they get the Withdrawal Bill through after that?
"How do they get all the other legislation that needs to get through the House of Commons?
"You don't actually have to call a general election without realising how difficult this would put the government's position in."