Brexit talks have frequently run into problems over goods crossing between Northern Ireland and the Republic of Ireland, and therefore the EU. Ministers have now called on the EU to renegotiate the Northern Ireland protocol, the terms of which were agreed by the EU and the British government in 2019.

       On July 21 Brexit negotiator David Frost and Northern Ireland Secretary Brandon Lewis sketched out plans in a “command paper".

       This paper says the Northern Ireland protocol has proven unworkable in practice and so they are calling for renegotiations of this part of the Brexit deal.

       The EU has so far rejected calls to look again at the terms of the protocol.

       The European Commission responded in a statement: “We are ready to continue to seek creative solutions, within the framework of the Protocol, in the interest of all communities in Northern Ireland.”

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       They firmly added: “However, we will not agree to a renegotiation of the Protocol.”

       The British Government is now seeking to come to a more productive settlement with the EU over the protocol as numerous problems have arisen since its implementation.

       The Northern Ireland protocol seeks to soften the land border between Northern Ireland and the Republic of Ireland, which is still a member of the EU.

       It helps prevent custom checks between the Republic of Ireland and Northern Ireland, which officials fear would create friction and even a return to the tensions and violence that have characterised much of Northern Ireland's past.

       But, the protocol as it currently stands means that further checks have been made on goods travelling between Northern Ireland and other parts of the UK.

       Critics have said this essentially creates a border in the Irish Sea which has angered unionists and businesses. There is evidence that it has fuelled tensions during this year's marching season, often a flashpoint in Belfast and Londonderry.

       There are concerns that the EU’s refusal to enter into renegotiations could lead to a stand-off.

       It is feared that the UK may have to make concessions to the EU to relax what unionists see as a border in the Irish Sea, such as keeping the UK’s food standards in line with the EU’s.

       James Smith, an economist at ING told CNBC: “With trust between both sides clearly low, the bigger near-term question is whether further legal steps are taken by Brussels that eventually culminate in tariffs – and in a negative scenario, some form of a mini trade war.”

       Mr Lewis called for the EU to reconsider. Writing in the Irish Times he said: “The situation is now urgent. The UK and Ireland have a huge, and very direct, interest in finding solutions here.

       “But we need constructive and ambitious discussions with the EU which deal with the actual reality.”

       He added: “We need to find a way forward, a new balance of arrangements, adapted to the practical reality of what we have seen since January, and based on the common interests we all share.”