The European Commission has published its first formal paper on how it believes Britain should deal with Irish issues in the Brexit negotiations.
In a four-page document on the critical issue for the island of Ireland, negotiators in Brussels have warned that it is more than just a customs problem.
They said they were not offering solutions on how cross-border trade and travel will be protected on the island of Ireland and the onus was on the UK to come up with ideas to avoid a hard border, including checkpoints.
The EU's chief negotiator, Michel Barnier, has said that "a unique solution" was needed to deal with issue of the border between the Republic and Northern Ireland.
He said he was worried by the UK position on the Irish border and insisted that the EU will not let the UK use the border as a "test case" for wider UK-EU border arrangements.
Mr Barnier said he was concerned over the UK government's position on Ireland, which appeared to envisage the EU suspending the application of its laws, single market and customs union at a new external border.
"What I see in the UK paper on Ireland and Northern Ireland worries me," he told a Brussels press conference.
"The UK wants to use Ireland as a kind of test case for the future EU/UK customs relations. This will not happen.
"Creativity and flexibility can't be at the expense of the integrity of the single market and customs union.
"This would be not fair for Ireland and it would not be fair for the European Union."
He also said the EU is ready to speed up divorce talks.
"Given the passing time, and this passing time worries me, I am ready to accelerate, to intensify the rhythm of talks," Mr Barnier told reporters.
The paper says: "It is the responsibility of the United Kingdom to ensure that its approach to the challenges of the Irish border in the context of its withdrawal from the European Union takes into account and protects the very specific and interwoven political, economic, security, societal and agricultural context and frameworks on the island of Ireland.
"These challenges will require a unique solution which cannot serve to preconfigure solutions in the context of the wider discussions on the future relationship between the European Union and the United Kingdom."
EU's lead Brexit negotiator Michel Barnier outlines the commission's priorities regarding Ireland as he speaks to reporters in Brussels pic.twitter.com/sNLmjs51iY— RTÉ News (@rtenews) September 7, 2017
The Brussels document warned that a thorough understanding of the issues beyond customs rules is needed to move negotiations forward.
The paper called for the negotiations to secure a political commitment to protect the Good Friday Agreement and the gains of the peace process.
It said these gains need to be strengthened, including the societal benefits and the normalisation of community relations in Northern Ireland and north-south.
"Flexible and imaginative solutions will be required to avoid a hard border, including any physical border infrastructure," the paper states.
"This must be achieved in a way which ensures that Ireland's place within the internal market and Customs Union is unaffected."
The Irish Government said: "Our priorities remain protecting the Good Friday Agreement and the peace process, including by avoiding a hard border, and maintaining the Common Travel Area."
It called on the UK government to make "substantive commitments and workable solutions" to the question of the Irish border.
"The principles reflected in this paper must underpin any arrangements and solutions to be proposed, developed and agreed in future negotiations," the Government said.
The Brussels paper warned that the UK and Europe will have to assess how north-south cooperation could be impacted if and when EU law ceases to apply in Northern Ireland and whether specific provisions need to be made for this.
Mr Barnier's team called on the UK to make sure people's rights under the Good Friday Agreement are not affected, including by protecting against discrimination.
They said Irish citizens living in Northern Ireland must keep their rights as EU citizens.
They called for both London and Brussels to commit to paying what is due under peace dividend funding programmes.
The Brussels paper also described the Common Travel Area, which dates back to the 1920s, as a fundamental right which should be maintained. It said it underpins the peace process.
Earlier, British Brexit Secretary David Davis insisted discussions with Brussels on border plans have been "good" but Mr Barnier, said "a lot more substantial work" needs to be done.
In the minutes of the 12 July meeting, Mr Barnier is recorded as saying the UK "had not yet really engaged in the negotiations" and voicing concern that Mr Davis "did not regard his direct involvement in these negotiations as his priority".
Asked about the comments at the Brussels press conference, Mr Barnier said he had known Mr Davis for 20 years and had "cordial relations with him still and good professional relations".
He pointed to his own comments at a press conference at the end of the most recent round of Brexit talks in August.
"I paid tribute to his professionalism and the competence of the whole of the UK team, and I have nothing further to add," said Mr Barnier.
Taoiseach Leo Varadkar has said that he is "very happy" with the European Commission's paper.
He said the Irish Government wants Britain to stay within the Customs Union - or something very similar to it - for a transitional period after leaving the EU.
The Joint Committee on European Union Affairs also welcomed the publication of the EU report.
Committee Chairman, Michael Healy Rae said: "It is clear that the unique circumstances on the island of Ireland, in particular the Good Friday Agreement and the Common Travel Area, are fully recognised, which is very much appreciated."
Britain must ensure delicacies like Parma ham keep protected status
The EU paper states that Britain must ensure that European delicacies like Parmesan cheese, Parma ham and Champagne continue to have protected status after Brexit.
The position paper on intellectual property rights said the British government should put in place the "necessary domestic legislation" so the products continue to enjoy protected status after the UK's expected exit in March 2019.
This should not result in financial costs for the producers of the goods and administrative burdens should be "kept to a strict minimum", the paper states.
The European Commission first acted in 1992 to establish a list of products which could only be described by their place of origin if they really were produced in that place.
The UK list includes Whitstable oysters, Orkney beef, Shetland lamb, Kentish ale, Cornish clotted cream, Dorset Blue cheese, and Jersey Royal potatoes.
The same legal protection is accorded to Italian Parma ham, French Champagne and other European goods.