Ireland’s deputy premier has warned the UK there will be no Brexit withdrawal deal without an agreement on the Irish border.

Ahead of a visit by European Commission President Jean-Claude Juncker to Dublin, Tanaiste Simon Coveney indicated that a no-deal scenario was now being seriously contemplated within the EU.

“This is a question many people are asking,” he said.

David Cameron meets Jean-Claude Juncker
European Commission President Jean-Claude Juncker is making a two-day visit to Dublin (Suzanne Plunkett/PA)

Mr Coveney said the EU was standing firmly behind Ireland and its demand for legally binding assurances from the UK to ensure no return to a hard border on the island.

“We have been reassured over and over again that Ireland will not be left isolated here,” he said.

Mr Coveney added: “Let’s be very clear – there will be no withdrawal agreement, no transition agreement and no managed Brexit if the UK don’t follow through on their commitments.”

Mr Juncker arrived in Dublin on Thursday morning for a two-day visit as the impasse between the EU and the UK over the border continues.

Coming a week ahead of a crunch European Council meeting of leaders in Brussels, the visit 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.

Leo Varadkar
The Taoiseach will host an official dinner for Mr Juncker at Dublin Castle (Paul McErlane/PA)

Mr Juncker started his visit with a meeting with Taoiseach Leo Varadkar and Mr Coveney at Government Buildings. He will later receive an honorary doctorate from the National University of Ireland and attend an official dinner hosted by Mr Varadkar in Dublin Castle.

Later on Thursday morning he will address a joint sitting of both houses of the Irish parliament, the Oireachtas.

On Friday, he will meet Irish President Michael D Higgins and visit the home of the Gaelic Athletic Association (GAA), Croke Park, and the GAA museum.

He will also watch a demonstration of Gaelic football and hurling.

Sport – GAA All Ireland Championship – Final – Kilkenny v Galway – Croke Park
The European Commission President will visit Croke Park (Niall Carson/PA)

Rules governing the border post-Brexit represent one of the most vexed issues facing the negotiators in Brussels.

Advances have been made in a number of areas, such as customs, VAT and nuclear waste regulation, EU chief negotiator Michel Barnier has said, but “a lot more work” needs to be done to meet the October deadline.

Mr Juncker will be accompanied on his engagement in Dublin on Thursday morning by Mr Barnier and EU agriculture commissioner Phil Hogan.

Mr Varadkar has suggested other countries will baulk at signing trade deals with the UK post-Brexit if Prime Minister Theresa May fails to honour commitments made to the EU on the Irish border issue.

Both sides have agreed to include a so-called “backstop” option in the withdrawal 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.

On Wednesday, the European Parliament’s chief Brexit co-ordinator told MPs the UK plan for a temporary customs backstop was “not acceptable” and any fall-back option cannot be time-limited.

Guy Verhofstadt said the Government’s position that the backstop of continuing UK alignment with the EU customs union would cease by the end of 2021 if no other solution was found left him “puzzled”.

Ahead of Mr Juncker’s arrival in Dublin, the Taoiseach said: “This is an important opportunity to assess the state of play in the Brexit negotiations.

“We need to see much more progress from the UK to implement the commitments they made in December and March, and I expect the UK’s efforts to intensify in the period ahead.”

He added: “President Juncker and I are both very committed to the European project and the benefits that it brings to citizens across the Union.

“We will also discuss other key items on the agenda of next week’s meeting of the European Council such as trade, ensuring a stable euro, and equipping the Union with a budget for its future needs.”