As part of the Withdrawal Agreement, the two sides signed an agreement on Northern Ireland known as the Northern Ireland Protocol. The aim is to prevent the creation of a trade border on the island of Ireland, whether or not the two parties agree on an agreement on a future relationship. This required finding a way to control and monitor goods entering Northern Ireland from the rest of the UK so that they could then enter the republic freely without jeopardising the EU`s single market. To this end, the Protocol suggests that certain controls be carried out on products when they cross the Irish Sea from Great Britain to Northern Ireland in order to ensure safety standards, in particular in the field of food and live animals, and to carry out the necessary customs controls. The North will continue to apply EU single market rules in some areas, although it remains in the UK customs union. The practical operation of these agreements was negotiated in a separate committee on the main negotiations, although the final agreement on trade rules between Great Britain and Northern Ireland is strongly influenced by the adoption of a comprehensive trade agreement. The protocol also states that after four years, Northern Irish politicians must be asked to give their consent to the continuation of the new agreements. That would require a vote in the House. If there is a positive vote, then the question would come back to a decision after another four or eight years, if the vote includes a sufficient number of unionist and nationalist communities. If the vote is against the agreements, there will be a two-year reflection period during which an EU/UK committee will examine how to proceed, respect the Belfast agreement and make recommendations. In the run-up to the general elections on 12 December 2019, the Conservative Party committed to leaving the EU with the withdrawal agreement negotiated in October 2019. Labour has promised to renegotiate the above deal and hold a referendum where voters can choose between the renegotiated deal and Remain.
The Liberal Democrats promised to repeal Article 50, while the SNP intended to hold a second referendum, but repealed Article 50 if the alternative was a no-deal exit. The DUP supported Brexit but would try to change the parts of Northern Ireland it was not happy with. Plaid Cymru and the Green Party backed a second referendum, saying Britain should remain in the EU.