The intervention from Downing Street comes the day after Lord Frost threatened to trigger Article 16 of the Protocol if Brussels failed to engage in talks. Westminster and Brussels have been at loggerheads over problems caused by the Protocol in Northern Ireland since the start of the year.

       Unionists have accused the EU of being "purist" in its implementation of customs checks on goods travelling from Britain to the province and undermining the UK's internal market.

       Lord Frost published his plan to redraw the Protocol in July to help ease frictions but so far the proposals have been rejected by the European Commission.

       This afternoon, the Prime Minister's official spokesman admitted there had been "elements of progress" in talks over the summer but said serious problems remained.

       "We have made elements of progress. You've seen that we have indefinitely held some of the checks that were due to come in," he said, referring to the decision to suspend bureaucratic red tape imposed by the EU on goods crossing the Irish Sea.

       Urging Brussels to now start urgent talks on more long-term reform, he added: "With regards to the Protocol, at its core, we still feel there needs to be a full negotiation.

       "That needs to begin seriously and begin soon.

       "It mustn't be the EU coming up with its own plan and solution and presenting them as 'take it or leave it'.

       "We are very much looking forward to continuing those discussions."

       The European Commission is expected to outline by the end of September plans that could ease the movement of goods from Britain to Northern Ireland in an effort to ease tensions resulting from Brexit.

       Vice President Maros Sefcovic, last week promised "creative and solid new solutions" under the current deal.

       More to follow...