The UK and the European Union

The UK stopped being a member of the EU on 31 January 2020. It then entered a transition phase (outside the political institutions, but still inside the single market and customs union) until 11.00pm on 31 December 2020. Since then its relationship has been government by the Withdrawal Agreement, ¹⁹ https://commission.europa.eu/strategy-and-policy/relations-united-kingdom/eu-uk-withdrawal-agreement_en  approved by parliament in January 2020 (but some aspects on trade between Great Britain and Northern Ireland were modified in 2023 by the Windsor Framework ²⁰ https://www.gov.uk/government/publications/the-windsor-framework  negotiated by Rishi Sunak) and the Trade and Cooperation Agreement (TCA) negotiated by Boris Johnson’s government.

The TCA is a deep free trade agreement which provides for (generally) tariff-free trade between the UK and the EU. But it still introduced a lot of friction into the trade relationship through the reintroduction of non-tariff barriers and the necessity for customs paper-work. The Johnson government prioritised regulatory autonomy for Great Britain over integration into the EU market and negotiated a deal that secured this outcome.

The Starmer government agreed a new security and defence partnership ²¹ https://commission.europa.eu/strategy-and-policy/relations-united-kingdom/eu-uk-trade-and-cooperation-agreement_enhttps://assets.publishing.service.g…  with the EU on May 19th 2025 as part of its reset of EU/UK relations. It also agreed to extend the agreement reached by the Johnson government on fisheries for a further 12 years (it was due to expire in June 2026) and has concluded a long outstanding agreement on Gibraltar.

What are the current government’s plans to change the relationship?

The Common Understanding, ²² https://www.gov.uk/government/publications/ukeu-summit-key-documentation/uk-eu-summit-common-understanding-html  reached at the 2025 summit, set off negotiations under various headings. There were three areas where the UK government said it would agree to “dynamically align” with EU rules in return for creating a common sanitary and phytosanitary area to make trade in agricultural and other food and animal products much easier, allow the UK to link to the EU emissions trading scheme and participate in the EU energy market. Those negotiations are not – yet – concluded but the government has announced legislation to allow dynamic alignment. The government also committed to negotiate a “youth experience scheme” with the EU to allow easier movement of under 30s between the UK and the EU. The UK has already rejoined the Erasmus scheme for next year but negotiations on UK participation in the SAFE defence procurement programme failed last November.

The current chancellor and PM have both signalled that they want to move closer to the EU in economic relations, but no concrete plans have been forthcoming yet.

If the UK wanted deeper integration, what options are there?

In theory the UK could seek membership of the European Economic Area (like Norway, Lichtenstein and Iceland, who all participate in the European Single Market). They do, however, accept EU rules without a direct say in the Council or in the European Parliament, accept freedom of movement and make budget contributions. However, they remain outside the customs union, and do not participate. If the UK did seek to join it would first need the agreement of the EFTA states to join the European Free Trade Area and then it would need their agreement and that of all EU member states to join the EEA.  Any individual state would have a veto. ²³ https://researchbriefings.files.parliament.uk/documents/CBP-8129/CBP-8129.pdf

Another model is the Swiss model of selective participation in the single market where a new agreement was concluded after long and tortured negotiations and critically commits the Swiss to dynamic alignment in areas of participation and and introduces a new dispute resolution mechanism ²⁴ https://ukandeu.ac.uk/the-swiss-model-a-special-relationship-to-the-european-union/ . But the Swiss accept free movement, with safeguards, and make budget contributions. This agreement is still subject to ratification in Switzerland which means a referendum – and that is far from guaranteed. This may be the sort of model the government would seek to develop over time – but at least until the Swiss have ratified the EU is unlikely to be up for negotiating this type of arrangement with the UK, particularly if the UK maintained its free movement red line.

While none of these countries form a customs union with the EU, the UK could also separately seek to form a customs union with the EU. Turkey has a customs union in manufactured goods with the EU (only EU members states can be in the customs union). This would remove the need for customs documentation for trade with the EU but would mean accepting the EU common external tariff and probably force the UK to give up the FTAs it had negotiated since Brexit – it would need to try to access the deals the EU has negotiated. It is also far from guaranteed that the UK would have a say on future EU trade deals where the EU could offer market access to the UK and could risk being in the same position as Turkey which  has to open its markets to countries that the EU has negotiated trade deals with without any guarantee of reciprocal access.

It is also possible that a new model emerges in the negotiations over EU membership for Ukraine. Ukraine already has an association agreement with the EU, which allows for access to the single market in return for integration in specific areas. Many EU member states are concerned about free movement for Ukrainians.

Of course, the EU could also develop a new model for integration of the UK or the UK could propose one. But neither side appears to have developed a model for a new “bespoke” relationship (though that the EU has already crossed some of its own red lines to find a way forward on Northern Ireland).

Could the UK rejoin the EU?

Any European state which meets the EU’s “values”  European Union can apply under the process set out in Article 49 of the Treaty on the Functioning of the EU. The criteria are:

• stable institutions guaranteeing democracy, the rule of law, human rights and respect for and protection of minorities;
• a functioning market economy and the capacity to cope with competition and market forces in the EU;
• the ability to take on and implement effectively the obligations of membership, including the aims of political, economic and monetary union.

There is then a staged process to go through – which involves application, a recommendation from the Commission, acceptance by the Council to give that nation “candidate status” (a decision which requires unanimity), then accession negotiations, followed by final agreement which again requires unanimity in the Council.

So, the UK could certainly reapply. It is not guaranteed that the UK would be accepted as a candidate country, especially if it looks as though there is a shaky domestic basis for application. Various ministers across the EU have indicated they would welcome the UK rejoining if it accepted all the obligations of membership and it would arguably be much easier to negotiate than a “special” relationship.

As a member state, the UK had negotiated a budget rebate and opt-outs in various areas including from euro membership and membership of the Schengen area. There would be no guarantees any or all of these would be replicated in new accession negotiations.

Could the UK rejoin without a referendum?

There is no requirement to have a referendum, and London mayor Sadiq Khan has argued that a future Labour government which had committed to rejoin in a manifesto need not have a referendum. But a referendum would cement UK membership more securely (if won) and since the decision to leave was taken in a referendum, there would be huge pressure to put rejoining to a referendum.