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Irish backstop

The Northern Ireland backstop was an arrangement for the Irish border that was part of Theresa May’s Brexit deal.

Irish and EU flags

What is the Northern Ireland backstop?

The Northern Ireland backstop was an arrangement for the Irish border that was part of Theresa May’s Brexit deal. It would have come into effect if no other solutions to maintain the current open border were agreed once the UK had left the EU. It was intended to protect the Good Friday Agreement/Belfast Agreement and keep an open border between Northern Ireland and Ireland after Brexit.

Both the UK and EU agreed on the need for a backstop to ensure no hard border – physical checks and infrastructure – returns to Ireland. However, when Boris Johnson became prime minister in July 2019 he managed to obviate the need for a backstop by agreeing a permanent new relationship between Northern Ireland and the EU. This new relationship means Northern Ireland is treated differently to the rest of Great Britain and following EU rules in some areas.

Why might the border have hardened as a result of Brexit?

The UK’s decision to leave the EU single market and customs union means that it will become a ‘third country’ to the EU. If the UK and EU had failed to find a new arrangement, the Irish land border would have become a customs and regulatory border involving the standard checks it has at its border with any third country.

How did the border feature in the withdrawal negotiations?

The EU guidelines for the first phase of negotiations on UK withdrawal identified the "unique circumstances on the island of Ireland". The guidelines also stated that avoiding a hard border was one of three key issues that needed to achieve ‘sufficient progress’ in phase one of negotiations – along with the financial settlement and citizens’ rights – to allow talks to begin on the framework for the future relationship between the UK and the EU.

The UK initially argued that the border could only be fully solved through the future UK–EU relationship. However, the EU, particularly the Irish government, wanted legally binding commitments to avoiding a hard border included in the Withdrawal Agreement setting out the terms of the UK’s exit from the EU.

In the run up to the critical December 2017 European Council, the question of the Irish border became critical to the prospect of successfully achieving ‘sufficient progress’. The two sides were forced to reach an agreement and bridge the gap between their positions.

What was agreed in the December 2017 Joint Report?

In December 2017, the two parties agreed in the Joint Report that to avoid a hard border, there are three possible solutions:

  • To achieve this objective through the overall UK–EU relationship agreed after the UK leaves the EU. This is the UK’s preferred option.
  • Should this not be possible, the UK will propose specific solutions to allow for a special post-Brexit arrangement for Northern Ireland.
  • In the absence of agreed solutions being reached before the transition period is scheduled to end in December 2020, the UK will maintain full alignment with the rules of the internal market and the customs union which, now or in the future, should support North–South co-operation, the all-island economy and the protection of the 1998 Good Friday Agreement/Belfast Agreement. This arrangement would remain in place until alternative solutions, most likely relying on advances in technology, could be introduced.

Through this agreement, the UK effectively conceded that a legally watertight solution to the border question had to be included in the Withdrawal Agreement, rather than postponed to the future relationship negotiations. This form of words allowed both sides to recommend that the requisite ‘sufficient progress’ had been made for further talks to take place, on the framework for the future UK–EU relationship. The European Council, including the Taoiseach (the Irish prime minister) duly signed this off in December 2017.

What happened after the Joint Report?

While the two sides agreed on the wording of the Joint Report, there was a lack of agreement on what the proposed solutions meant in practice. The focus of discussions on the border shifted to the third proposal, which became known as 'the backstop'.

In February 2018, the European Commission published a draft withdrawal agreement which, to deliver the backstop, proposed keeping Northern Ireland within the EU customs territory and ‘common regulatory area’ covering goods and sanitary and phytosanitary regulations. This approach, a ‘Northern Ireland specific’ backstop, would require customs and regulatory checks between Great Britain and Northern Ireland if it ever came into force.

Then Prime Minister Theresa May said “no UK prime minister could ever agree to” this proposal because it would threaten the “constitutional integrity of the UK”. The UK’s preferred approach was for any backstop to apply to the whole of the UK, not just Northern Ireland, to prevent the need for checks to take place on goods moving from one part of the UK to another.

In summer 2018, the UK government published proposals for a temporary UK-wide customs union with the EU and, as part of its suggestions for the future relationship, a ‘common rulebook’ on goods regulations. Effectively the UK argued that the backstop was unnecessary as the future relationship would ensure there was no need for a hard border. However, the EU rejected the time-limited proposal and the idea of a UK-wide backstop, as it would prejudge the outcome of detailed future relationship negotiations.

Over summer 2018 discussions continued on the backstop, with Michel Barnier, the EU's Chief Negotiator for Brexit, attempting to 'de-dramatise' the issue by making clear that the EU’s proposal would require "only technical controls on goods". The EU also sought to limit the categories of goods facing checks, building on existing animal health checks that take place between the two islands, rather than creating lots of new checks. 

But there was no concrete progress in mid-2018. The EU’s priorities were reasserted at the Salzburg summit in September 2018, when European Council President Donald Tusk said “there will be no Withdrawal Agreement without a solid, operational and legally binding Irish backstop”.

The two sides reached agreement on a draft Withdrawal Agreement in November 2018, which included a protocol on Northern Ireland setting out the backstop. The EU made a significant concession in granting a UK-wide ‘single customs territory’, avoiding the need for customs checks between Great Britain and Northern Ireland, while the requirement for regulatory alignment is limited to Northern Ireland.

Why were there concerns about the backstop?

The backstop proved one of the most contentious issues in parliamentary debates on the draft Withdrawal Agreement. The Democratic Unionist Party (DUP) opposed it because it would have introduced differences in regulation between Northern Ireland and the rest of the UK, which it saw as a threat to Northern Ireland’s place in the Union.

A majority of people in Northern Ireland supported the backstop, however, as it gave them privileged access to both the UK and EU markets. In January 2019, the UK government published proposals on how the UK, including the Northern Ireland executive, could influence both the decision to use the backstop and its governance if it came into effect, as well as a commitment that the rest of the UK would unilaterally align with the single market regulations being applied in Northern Ireland.

Other Brexiteers are opposed to the backstop because it would mean the UK remaining in a customs territory with the EU, removing the UK’s ability to vary its tariffs, a key component of trade deals.

There were also concerns that the UK would not be able to leave the backstop. It was intended to apply “unless and until” alternative arrangements, which both sides agree on, can replace it.

What happened when Boris Johnson became prime minister?

Theresa May resigned in summer 2019 after parliament continued to reject her deal, with the backstop cited as the key issue. Boris Johnson became prime minister pledging to scrap the backstop altogether.

Johnson wrote to the EU declaring the backstop was "anti-democratic", "inconsistent with the UK’s final destination" and risked "weakening the delicate balance of the Good Friday Agreement". The UK government put forward a formal proposal to the EU, which included Northern Ireland following EU rules in agrifood and creating a customs border between Northern Ireland and the EU/Republic of Ireland.

Following negotiations, the two sides agreed the new Ireland/Northern Ireland protocol, which involves Northern Ireland following EU rules for goods and customs but included a consent mechanism. The deal looked similar to the one first proposed by the EU in February 2018, which was rejected by the UK, but now including an exit mechanism. 

Timeline of negotiations on the Irish backstop

  • March 2017: Prime Minister Theresa May triggers Article 50, beginning the countdown to Brexit
  • April 2017: European Council issues its first guidelines for Brexit negotiations, which establish the "aim of avoiding a hard border"
  • June – December 2017: Phase one negotiations, including discussions on the Irish border
  • December 2017: Joint UK–EU Report published on phase one of negotiations, establishing idea of a backstop that will be used "in the absence of agreed solutions" to avoid a hard border and that must be included in the Withdrawal Agreement
  • February 2018: EU publishes draft Withdrawal Agreement, suggesting that if no other solutions are found, Northern Ireland would remain "part of the customs territory" of the EU
  • February 2018: Theresa May says "no UK prime minister could ever agree" to the EU’s proposals
  • June 2018: UK publishes proposal for "temporary customs arrangement" to apply to the whole UK in the event of no other solution being found, avoiding the need for customs checks between UK and EU
  • July 2018: UK publishes 'Chequers' white paper, which proposes ‘common rulebook’ on goods to avoid regulatory checks at borders
  • September 2018: Salzburg summit – EU confirms that "while there are positive elements in the Chequers proposal, the suggested framework for economic co-operation will not work" and that "a solid, operational and legally binding Irish backstop" is still necessary
  • September 2018: Theresa May says the UK will "set out our alternative" solution to the backstop
  • October 2018: European Council fails to deliver Withdrawal Agreement
  • November 2018: Special Council agrees draft Withdrawal Agreement
  • December 2018: The UK government delays ‘meaningful vote’ on Withdrawal Agreement
  • January 2019: The UK government publishes ‘reassurances’ on the backstop and exchanges letter with EU Council and Commission presidents, setting out joint ambition to avoid backstop through future relationship
  • January 2019: Parliament rejects the government’s deal in a second 'meaningful vote'
  • January 2019: Parliament approves the 'Brady amendment', seeking changes to the backstop
  • February 2019: Further negotiations between Stephen Barclay, then secretary of state for exiting the EU; Geoffrey Cox, then attorney general; and the EU
  • March 2019: The UK government and the EU publish 'joint instrument' on the backstop; Cox publishes legal advice
  • August 2019: Boris Johnson’s government writes to the EU outlining concerns with the backstop
  • September 2019: The UK puts forward a proposal for replacing the backstop
  • October 2019: The UK and EU agree a new Ireland/Northern Ireland protocol
Country (international)
European Union
United Kingdom
Northern Ireland
May government
Devolved administration
Northern Ireland executive
Public figures
Theresa May
Institute for Government

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