Amidst unprogressive negotiations, EU’s Brexit chief negotiator, Michel Barnier has berated U.K.’s position on the Irish border, Bloomberg reports.

Speaking to reporters in Brussels on Thursday, Barnier said, “What I see on the U.K.’s paper on Ireland and Northern Ireland worries me. “The U.K. wants to use Ireland as a kind of test-case for the future EU-U.K. customs relations – this will not happen.”

The European Union is publishing series of papers this week highlighting its Brexit position and its approach to existing issues including the Irish border. Barnier and other notable EU officials are casting doubt over whether the level of Brexit negotiations which they branded unprogressive will be enough to enable leaders at the forthcoming EU summit to open discussions on future trade links with the U.K.

“Creativity and flexibility cannot be at the expense of the integrity of the single market and customs union. This would not be fair for Ireland and would not be fair for the European Union.”

The position paper reveals the EU’s convictions that, “it’s the responsibility of the United Kingdom” to ensure that Brexit protects the special “political, economic, security, societal and agricultural context and frameworks on the island of Ireland.”

Both the EU and UK had earlier agreed they would make concerted efforts to avoid a resolve that will degenerate into a hard border between Northern Ireland and Ireland as such was the state of the border before the crisis that rocked both countries was resolved through a peace process in the 1990s.