The Democratic Unionist Party has accused the Irish Government of "shutting down any possibility of a breakthrough" on the contentious backstop.
Deputy DUP leader Nigel Dodds said the backstop remained the "poison" affecting any vote on the Brexit Withdrawal Agreement in the House of Commons.
British Prime Minister Theresa May said yesterday the Commons will vote on the deal around January 15, despite speculation it could be delayed for a second time.
Mr Dodds blamed the EU and the Irish Government for rejecting efforts to rewrite the deal or find a compromise.
"The responsibility for this lies primarily with the EU," he said.
"EU spokespersons have gone out of their way to reiterate that there will be no renegotiation of the Withdrawal Agreement.
"True to form the Dublin Government has quickly shut down any possibility of a breakthrough by its now familiar tactic of a fast and flat rejection of any form of compromise."
He said it was time for the UK to make clear what it wants for the Withdrawal Agreement to pass the Commons, "so that the EU is in no doubt as to what's required for a deal".
"The backstop remains the poison which makes any vote for the Withdrawal Agreement so toxic," he said.
"The EU has shown in the past that it will move, but only if faced with a resolute red line on the part of the UK government."