The paper says 'all parts' of the Good Friday Agreement must be protected
The European Commission says it is the responsibility of the UK to protect the Irish border.
Its Brexit Task Force has issued a Guiding Principles paper on Ireland in the context of Brexit negotiations.
In it, the commission 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."
The paper adds that the Good Friday Agreement needs to protected "in all its parts" - including the Common Travel Area and avoiding a hard border.
"As an essential element of the withdrawal process, there needs to be a political commitment to protecting the Good Friday Agreement in all its parts, to protecting the gains of the peace process, and to the practical application of this on the island of Ireland."
It says "flexible and imaginative solutions will be required, including with the aim of avoiding a hard border."
"Ensuring the avoidance of a hard border on the island of Ireland is central to protecting the gains of the peace process underpinned by the Good Friday Agreement."
The EU's chief Brexit negotiator, Michel Barnier, told a press conference in Brussels: "The solution for the border issue will need to be unique.
"It cannot preconfigure the future relationship between the European Union and the UK. It will require both sides to be flexible and creative.
"What I see in the UK's paper on Ireland and Northern Ireland worries me.
"The UK wants the EU to suspend the application of its laws, its Customs Union, and its Single Market at what will be a new external border of the EU.
"And 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 cannot be at the expense of the integrity of the Single Market and the Customs Union.
"This would not be fair for Ireland and it would not be fair for the European Union."
The Government says it welcomes the paper, adding: "The paper clearly reflects the continuing close engagement between Ireland and the EU Task Force and builds on the European Council Guidelines and subsequent negotiation mandate, in which Ireland’s concerns and priorities were strongly acknowledged.
"Our priorities remain protecting the Good Friday Agreement and the peace process, including by avoiding a hard border, and maintaining the Common Travel Area."
"This week’s EU paper set out principles which will form an important basis for negotiating those solutions with the UK.
"As the Task Force’s paper makes clear, the principles reflected in this paper must underpin any arrangements and solutions to be proposed, developed and agreed in future negotiations."
The paper will be discussed by the EU27 countries later this month.
Read the European Commission paper in full here