Leo Varadkar holds firm on Brexit deal but ready to 'listen' to new UK proposals

However, senior Government figures continue to insist that the Brexit withdrawal agreement, which was signed off on by Mrs May and EU leaders last month, is not up for renegotiation.

"The withdrawal agreement won't be up for renegotiation but we will listen to what the UK government has to say," the senior Government source said.

Meanwhile, former European Commission president Romano Prodi said he believes the EU will come back to the negotiating table if the Brexit deal does not pass through the British parliament.

Mr Prodi's comments come ahead of a crucial vote in the UK parliament on Tuesday which will be followed by an EU leaders' summit in Brussels on Thursday.

Taoiseach Leo Varadkar is due to speak to president of the European Commission Jean Claude Juncker tomorrow ahead of the summit.

Last night, the senior source insisted there is "no panic" within the Government despite the uncertainly surrounding the Brexit vote in the House of Commons.

Asked if there was any leeway on the backstop agreement which ensures there is no hard border with Northern Ireland, the source said: "We'll always listen to suggestions or proposals but a unilateral exit can't be conceded."

"Listen means listen - it doesn't mean any more than that," the source added.

Hardline Brexit-backing Conservative Party MPs believe the current deal will leave the UK indefinitely tied to the European Union through the fall-back arrangement which ensures there will be no hard border.

They are seeking to rip up the current agreement including the Northern Ireland backstop to ensure Britain can leave the fall-back arrangement at their own discretion.

On Tuesday, the House of Commons will vote on the current withdrawal agreement and it is being widely speculated that Mrs May does not have the votes needed to pass the bill.

Mr Prodi said both Britain and the EU will work to ensure there is continued free trade after Brexit because it is in the interests of both jurisdictions. "The UK has no alternative - the EU is a large part of its trade. Always the problem of Northern Ireland, but it is possible. Common sense helps," he told the Observer newspaper.

Asked by the newspaper about the EU's refusal to entertain the possibility of further negotiations, Mr Prodi said: "Look, when the British parliament has still to vote, you are obliged to be in this position. But then of course the day after, you start dealing. This is politics."

However, speaking in the Dail last Wednesday, Taoiseach Leo Varadkar insisted there was no possibility of reopening Brexit negotiations even if Mrs May does not secure the support of her parliament for the withdrawal agreement.

"The suggestion that somehow if it is defeated, we would somehow find ourselves negotiating with a parliament really is quite unworkable," the Taoiseach said.

"To see a parliamentary delegation entering the tunnel to reopen the talks is just not something that is feasible," he added.

Meanwhile, Minister for Justice Charlie Flanagan said the Sinn Fein and dissident republican strategy of using Brexit to push for a border poll on a united Ireland is causing political instability within "loyalist enclaves" in Belfast which could lead to serious violence.

Speaking to the Sunday Independent, he said "conflating" Brexit with the possibility of a united Ireland referendum was "particularly dangerous".

"I have seen since Brexit some political instability within loyalism as a direct response to those on the republican side calling for a border poll as a precursor to a united Ireland," he said.

"I have to say to the dissidents, who are, along with Sinn Fein, speaking in terms of border polls, my response to them is we must abide fully with the terms and conditions of the Good Friday Agreement and in particular, the principle of consent, and I don't believe that the time is now ripe for a border poll," Mr Flanagan added.

He also said hundreds of dissident republican terrorists with links to Dublin-based drug gangs pose a major threat to the country's security if a hard border is erected in Northern Ireland as a result of a no-deal Brexit.