The European Union rejected a demand by the U.K. to renegotiate the Brexit deal governing Northern Ireland as tensions between the two sides escalate.

“Respecting international legal obligations is of paramount importance,” European Commission Vice President Maros Sefcovic said in a statement on Wednesday. “We will not agree to a renegotiation.”

Earlier on Wednesday, David Frost, the U.K. minister for EU affairs, called on the bloc to rip and substantially rewrite the controversial Northern Ireland Protocol, the part of the U.K.’s separation agreement that governs trade and market rules for the region.

Frost told the House of Lords “we cannot go on as we are.” He blamed the Protocol for causing “significant disruption” to trade between Northern Ireland and the rest of Britain and for causing “societal instability.” He warned the U.K. would be ready to trigger a clause suspending parts of the Protocol—a move that would dramatically increase tensions with the EU.

The U.K. has come under pressure from companies including Marks & Spencer Group Plc to find a solution to rules that businesses say are leading to delays in getting goods into Belfast. But any move to rip up a deal that Prime Minister Boris Johnson committed to less than two years ago risks further damaging trust in Britain among officials in Brussels.

The EU has long insisted that the Protocol must be implemented as originally designed. In March, the bloc began legal action against the U.K. after Britain unilaterally delayed enforcing part of the agreement.

Non-Starter?

In rejecting a renegotiation, Sefcovic said the EU will continue to engage with the U.K. to find “creative solutions” within the framework of the Protocol.

A European official said that the dispute between the two sides has been exacerbated by the fact that officials in Brussels don’t trust Frost and Johnson.

Speaking to the House of Lords, Frost conceded that relations so far have been “punctuated by legal challenges and characterized by disagreement and mistrust.”

Frost said that, as a first step, the EU must show it is serious about resolving the crisis.

To “ensure there is room to negotiate,” Frost called on the bloc to enter a “standstill period,” extending the current grace periods on regulations that allow chilled meats and other goods to be imported into Northern Ireland from the rest of the U.K.

He also said the EU should pause its legal action against the U.K. for not implementing the Protocol properly as a “genuine signal of good intent.”

Frost said the conditions exist to justify invoking Article 16 of the Protocol—the section which allows some of its rules to be suspended—but now is not the right time to do so.

The U.K. plan includes:

  • An honesty system for goods moving from Great Britain to Northern Ireland. Goods labeled “for NI” wouldn’t face customs checks, but those heading to the Republic of Ireland would.
  • A light-touch system for traders where they where they would provide information about their supply chains and shipments to the authorities, or risk spot checks.
  • Goods marked by U.K authorities as safe for sale in domestically would be allowed to be sold in Northern Ireland without having to prove that they also comply with EU rules.
  • The role of the European Court of Justice in enforcing parts of the protocol would be ended.