European Commission president Jean-Claude Juncker has warned the UK there will be no Brexit deal without agreement on the Irish border.

On a visit to Dublin, Mr Juncker said fellow EU member states would not let Ireland be “isolated” on the impasse, insisting the demand for a resolution was a Europe-wide demand.

Amid an ongoing stand-off over how to maintain a free-flowing border post-Brexit, Mr Juncker assured Taoiseach Leo Varadkar that the EU would not waver on what he made clear was a pivotal issue.

“This is not a bilateral question between Ireland and the United Kingdom – this is an issue between the UK and the European Union,” he said.

“We want to make it clear again and again that Ireland is not alone.

“We have Ireland backed by 26 member states and the commission – this will not change.

“I am strongly against any temptation to isolate Ireland and not to conclude the deal on Ireland.

“Ireland has to be part of the deal.”

Coming a week ahead of a key European Council meeting of leaders in Brussels, the visit to Dublin of Mr Juncker and the EU’s chief Brexit negotiator Michel Barnier is a clear demonstration of the EU’s solidarity with Ireland’s position.

This week the EU warned that more work was needed on how to deal with the 300-mile border between Northern Ireland and the Republic, the UK’s only land frontier with a European state, and protect frictionless movement after the withdrawal.

Both sides in the negotiations have agreed to include a so-called “backstop” option in any Brexit treaty, which would commit the UK to align with an EU regulatory framework in the absence of a wider trade deal.

But the shape of that fall-back remains a sticking point, with the EU rejecting a UK contention that it should only be temporary, even if a broader agreement fails to materialise.

After talks with Mr Juncker in Government Buildings in Dublin, Mr Varadkar said there was an urgent need to “intensify” negotiations to find an agreement on the shape of the border backstop.

“A withdrawal agreement without a backstop is of no use whatsoever,” he said.

He added: “Let me be blunt, there isn’t much time left if we are to conclude an agreement and have it operational by the time the United Kingdom leaves the European Union next March.”

Brexit talks in Dublin
Jean-Claude Juncker and Michel Barnier during talks in Dublin (Brian Lawless/PA)

Asked about wrangling within the UK Government over the customs issue, the Taoiseach said: “Internal British politics isn’t my concern.

“My job is to represent my country, Ireland, and to do that as part of the European Union and we remain at the heart of the European Union.

“The most important aspect of the withdrawal agreement for us is the backstop, and Prime Minister May committed in March that there would be a backstop and outlined in December what that backstop would contain.”

Later Mr Juncker addressed both houses of the Irish parliament, the Oireachtas.

He was applauded as he told members of the Dail and Seanad that “Ireland will come first” in the Brexit negotiations.

“There are those that think the other 26 countries will abandon Ireland for a deal that suits them,” he said.

“Ireland’s border is Europe’s border and it is our priority.”

Referring to the UK’s imminent departure from the EU, Mr Juncker told the Oireachtas that there is no deal as good as membership of the EU.

“It simply does not exist,” he said, adding that the prospect of the UK leaving the EU without any deal at all must be prepared for.

Addressing the joint sitting, Mr Varadkar said:

“The greatest challenge we face on this island is to unwrap the enigma, and solve the riddle of Brexit.

“It’s as tricky as it sounds, so we are grateful for the diligence and understanding shown by the Commission’s lead negotiator, Michel Barnier, in his conduct of these very difficult negotiations for the EU.”

He added: “We are so deeply grateful for the remarkable solidarity and support we have received from the EU institutions and fellow member states, none more so than from President Juncker.

“There has been consistent recognition of the unique position of Northern Ireland, and the unique situation in which it has been put by the decision of the UK to leave the EU.

Jean Claude Juncker
Jean-Claude Juncker (centre) receives an honorary doctorate during his visit to Dublin (Brian Lawless/PA)

“There is no stronger evidence of how small countries benefit so much from EU membership and how membership matters.”

Later, Mr Juncker received an honorary degree from the National University of Ireland. He became emotional during his address as he recalled his late friend and former EU Commissioner, Dubliner Peter Sutherland.

The Commission President’s final engagement of the day was a dinner at Dublin Castle hosted by Mr Varadkar.

The Brexiteer Democratic Unionists criticised Mr Juncker’s comments on Brexit, accusing the EU of using Ireland as a “bargaining chip” in the negotiations.

“Mr Juncker’s claim that ‘Ireland is not alone’ is false security for the country which would be most severely impacted by a no deal Brexit,” said DUP deputy leader Nigel Dodds.

“If Mr Juncker was really focused on helping Ireland, he would be encouraging the EU to focus on getting a post-Brexit trade deal in place.

“The Republic of Ireland is being used as a bargaining chip by the EU. This is a selfish interest.”

He added: “Rather than focus on backstop arrangements, Ireland would be better served by a sensible new trade deal which would work for the EU, the United Kingdom and, importantly, the Republic of Ireland.”

Mr Juncker will conclude his two-day visit to Dublin on Friday when he meets President Michael D Higgins at his official residence and then tours the Croke Park Gaelic Athletic Association (GAA) stadium.

A spokesman for the UK Government’s Department for Exiting the European Union said: “We’re committed to avoiding a hard border between Northern Ireland and Ireland, as well as avoiding any borders within our United Kingdom, and have set out our proposal on the customs element of a temporary backstop.

“This would only be used in very specific circumstances and be time-limited. It remains our intention to achieve a close economic partnership that does not require the backstop to be in operation.”