Michel Barnier has said the UK appears to be "backtracking" on its financial obligations, saying he is "very disappointed" by comments made recently.
The EU's chief negotiator held a press conference this afternoon in which he said the question of the divorce bill was "moral". The UK had committed to a seven-year budget under David Cameron, and should honour that.
Barnier added that the UK's plan to avoid all border controls on Ireland are "unacceptable". His comments come as the European Commission published a new position paper, stressing that the Good Friday Agreement continue to be protected "and strengthened in all its parts" after Brexit. It also wants the Common Travel Area to continue to be recognised.
The UK will be held responsible to put forward solutions to the issue of the Irish border, the European Commission added. "Given Ireland's unique situation in the Brexit negotiations, a unique solution is required," the paper said.
But on the border itself, it said the UK must come up with "flexible and imaginative solutions to avoid a hard border on the island of Ireland".
"These solutions must respect the proper functioning of the internal market and the Customs Union, as well the integrity and effectiveness of the EU's legal order," the paper added.
Michel Barnier, the EC's chief negotiator said, "Today's paper on Ireland and Northern Ireland is a concise and comprehensive text, which has been drafted in close cooperation with the Irish government. Our aim is to minimise the impact of the UK's decision to leave the EU for the island of Ireland. But as it was the UK's decision to leave the EU, it is the UK's responsibility to come forward with solutions to overcome the challenges for the island of Ireland."
The EC also released minutes from July in which Barnier was critical of Davis' no-show during talks.
The minute said he was concerned that "the United Kingdom had not yet really engaged in the negotiations or spelled out its positions. He noted in this regard that David Davis, the Secretary of State for Exiting the European Union, did not regard his direct involvement in these negotiations as his priority."