The European Commission has warned that gaps in British Prime Minister Theresa May’s new Brexit customs plan will lead to the creation of a hard border with Ireland.

Officials are worried the UK plan would not keep Northern Ireland aligned with single market rules. They are also concerned at UK proposals to time-limit the proposal until 2021 at the latest, with the presentation asking: “Is this a backstop?”

As reported by the Independent, the presentation concludes that the UK proposal “does not cover regulatory controls, leading to a hard border”.

However, the “backstop solution” is supposed to prevent a hard border from emerging on the island of Ireland no matter what happens. Both sides say they do not want a hard border because the open frontier is part of the Good Friday Agreement, which brought an end to the Troubles, reported the Independent.

Meanwhile, a spokesperson for the European Commission confirmed that European Commission chief negotiator Michel Barnier and the secretary of state for exiting the European Union David Davis met June 11 in Brussels to discuss the latest state of play of the Article 50 negotiations. “They touched on issues related to the withdrawal agreement, including the backstop for Ireland-Northern Ireland and the framework for the future relationship,” said the spokesperson.

In turn, a UK government spokesperson said: “The Prime Minster has been clear that we will never accept a customs border between Northern Ireland and the rest of the United Kingdom. We are also committed to maintaining the integrity of our own internal market. That position will not change.”