THE UK has broken a “great deal of trust” with the EU in the row over the Northern Ireland Protocol, the bloc’s chief negotiator has said.

European Commission vice president Maros Sefcovic told German news website Der Spiegel that problems with the Northern Ireland Protocol meant the UK “broke international law” in trying to get round the arrangement.

The protocol was a mechanism brought in to maintain a free-flowing land border on the island of Ireland after Brexit, which keeps Northern Ireland in the European single market.

Lord Frost, who has now resigned from his role as the UK’s Brexit negotiator and will be replaced by Foreign Secretary Liz Truss, had frequently threatened to trigger Article 16 - a mechanism in the protocol which allows one side to suspend the treaty rules unilaterally.

READ MORE: Boris Johnson reacts to fears over Scots Hogmanay revellers heading to England

However, the EU has warned that this would cause “serious consequences”, not just for EU-UK relations, but for Northern Ireland as well.

Frost resigned earlier this month, with Truss set to take up talks in January next year.

Sefcovic said that he is still confident a compromise can be found between the two sides, but that it would not be easy.

He told Der Spiegel he is “pragmatic” about Truss taking over post-Brexit negotiations, but warned that if she triggers Article 16 it would throw into jeopardy “the foundation of the entire deal” reached by the two sides.

The National:

Lord Frost (left) and Maros Sefcovic (right) during previous talks

Truss has said she remains prepared to invoke Article 16 if issues are not resolved.

Sefcovic said: “This is a very distracting element in the discussions. You try to achieve something together and – bam – there’s the threat of Article 16 again.

“It touches on the fundamentals of our relationship.

READ MORE: BBC admits fault after interview with Jeffrey Epstein's lawyer Alan Dershowitz

“The Northern Ireland Protocol was the most complicated part of the Brexit negotiations, and it is the foundation of the entire deal.

“Without the protocol, the whole system will collapse. We must prevent that at any cost.”

He added: “London has breached a great deal of trust, which we must first rebuild. But I believe we can find a compromise.

“The EU and the United Kingdom are strategic partners – and they should treat each other as such.”

A grace period for border checks and regulatory approvals for drugs expires at the end of the year.

The National:

Frost has resigned from his role as the UK's Brexit negotiator

The UK unilaterally extended the grace period, but there is a risk of trade disturbance for medicines if both sides don’t reach a deal by the end of January.

We previously told how Frost said in his resignation letter that he had “concerns over the current direction of travel” of the UK Government.

Frost claimed in his letter that Brexit is “secure” but that the UK Government’s challenge is now to “deliver on the opportunities it gives us”.