European Union's chief Brexit negotiator Michel Barnier addresses a news conference in Brussels, Belgium, Sept 7, 2017. [Photo/Agencies]

LONDON - The British government gave its first official response Thursday to a European position paper on the future of the border between Northern Ireland and the Republic of Ireland after Brexit.

The future of the border is critical as once Britain leaves the European Union (EU) it will be the only land border between the UK and the bloc.

Addressing the issue in Brussels, the EU's chief Brexit negotiator Michel Barnier said Britain wanted to use Ireland as a test case for future UK-EU customs relationship, but Barnier added: "this will not happen".

As he unveiled the EU paper on the Irish issue, Barnier referred to the British government's own position on future cross-border arrangements.

Barnier said: "What I see in the UK's paper worries me. Creativity and flexibility cannot be at expense of integrity of the single market. This would not be fair for Ireland and it would not be fair for the European Union."

He has called on Britain to come up with a unique solution to the border question.

In response, the British government said unilateral flexibility by the UK would not be sufficient to meet the shared objectives.

The government spokesman in London said: "We welcome the Commission's position paper on Northern Ireland and Ireland, which continues to demonstrate that the UK and EU's objectives on this issue are closely aligned."

"In particular, the commitment to avoid any physical infrastructure at the border is a very important step forward. As the UK's position paper set out, this is a crucial objective for the government, given the importance of the Northern Ireland peace process," the statement said.

"We were clear in our position paper that the nature of the border means that an agreed, reciprocal solution must be found...we welcome the Commission's continued recognition of the need for flexible and imaginative solutions," it said.