The December 2017 backstop agreement has been a topic of conversation in the UK and the EU since it was first introduced. This agreement is a temporary solution in the event that the UK and the EU are unable to agree on a long-term solution for the Northern Ireland border after Brexit.

The backstop agreement was first proposed in the Joint Report on progress during phase one of the Brexit negotiations. It states that if no long-term solution is reached by the end of the transition period, which is set to end on December 31, 2020, then a backstop will be implemented to ensure that there is no hard border between Northern Ireland and the Republic of Ireland.

The backstop would mean that the UK would remain in a customs union with the EU, and Northern Ireland would continue to follow EU regulations for goods. This would effectively create a regulatory border in the Irish Sea, which has been a point of contention for many in the UK.

Critics argue that the backstop undermines the integrity of the UK by creating a de facto border between Northern Ireland and the rest of the UK. It also raises concerns about the impact it will have on trade between Northern Ireland and the rest of the UK.

However, supporters of the backstop say that it is necessary to protect the Good Friday Agreement, which ended decades of violence in Northern Ireland. They argue that a hard border between Northern Ireland and the Republic of Ireland could lead to the return of violence in the region.

In November 2018, the backstop was included in the Withdrawal Agreement negotiated between the UK and the EU. However, the agreement has failed to be passed by the UK Parliament, leading to the current Brexit uncertainty.

The backstop remains a contentious issue in the Brexit negotiations, and its future is uncertain. However, it continues to be a key point of discussion as the UK and the EU work towards a resolution for the Northern Ireland border.