The EU chief negotiator for Brexit, Michel Barnier, has intensified the pressure on the UK to avoid a physical border with the Republic of Ireland if London wants to enter into a good trade deal with the EU.

Commenting on the British rejection of special customs rules that would separate Northern Ireland from the rest of the United Kingdom, an anathema for the Northern Ireland allies of Prime Minister Teresa May, Barnier noted the existing regulatory differences between the province and the kingdom. He also reaffirmed the bloc’s refusal to reach a special deal with the London City, insisting that once the UK leaves the European single market, British companies will still have access to it, but in worse conditions.

Before the summit next month, which will discuss the progress in divorce conditions, the Irish government has expressed concern that London has failed to explain how it plans to curb the island’s economic and social hardship. Dublin has expressed confidence that other EU countries support its demands for clarity.

Leaders fear that rebuilding the border could lead to renewed violence in the north after the 1998 peace treaty ceased the bloodshed that lasted for three decades.

Barnier said the EU could not compromise on the integrity of its single market and allow trade with Northern Ireland without customs if the British province did not join EU rules.

“Those who wanted Brexit must offer solutions”, insisted Michel Barnier.

The EU also expects London to come up with a more specific proposal on what financial commitments it will make when leaving and what EU citizens’ rights will be in the UK.