Debate on the UK applying to join the European Union

The petition calls for the UK to join the European Union as a full member as soon as possible. It had received over 132,500 signatures as of 18 March 2025.

The petition refers to the potential benefits of the UK joining the EU to boost the UK economy, increase its global influence, improve collaboration and provide stability and freedom.

Government response to petition

The government responded to the petition on 19 November 2024. It said that it had been elected on a manifesto that made clear “there will be no return to EU membership”. However, it said it was “determined to reset the UK-EU relationship” and put in on a more solid footing.

The government’s response to the petition gave details of its work to reset the UK-EU relationship. This includes efforts to secure a UK-EU security pact, involving cooperation on foreign policy and defence, and to address trade barriers.

In order to reduce border checks on food and agricultural products, the government has proposed a UK-EU sanitary and phytosanitary (SPS) agreement. It states that it is also working to help UK touring artists and to secure mutual recognition for professional qualifications “to help open up new markets for UK service exporters”.

The government’s response emphasises a commitment to constructive engagement with the EU, and to upholding existing UK-EU agreements. However, it stresses that the reset is not about “renegotiating or relitigating Brexit”, and that the government is not seeking to rejoin the EU single market or customs union or to return to freedom of movement with the EU.

Further details on the UK government’s reset with the EU, including the objectives it has set out, the EU reaction and commentary on proposals are provided in House of Commons Library briefing paper, Resetting the UK's relationship with the European Union

EU accession criteria

Applications to join the EU are made to the Council of the EU (ministerial representatives of each Member State) under Article 49 of the Treaty on European Union (TEU).

Article 49 TEU provides that EU membership is open to European countries that respect certain EU values set out in Article 2 TEU, relating to respect for human rights, democracy and the rule of law. Decisions on applications are taken unanimously by the Council after consulting the European Commission and receiving the consent of the European Parliament.

The European Council (EU heads of states and government) has set out criteria that countries seeking to join the EU need to meet, involving stable institutions guaranteeing democracy, a functioning market economy, and the ability to take on and implement the obligations of membership. EU accession negotiations focus on ensuring accession states are ready to implement the EU's body of law, with the European Commission issuing recommendations at different stages of the accession process regarding the candidate state’s alignment with EU rules and readiness to the join the EU.

The accession process can be lengthy, notably for states where there have been recent transitions to democracy and significant disparity with the EU in terms of economic development. However, where states have a similar level of economic development to existing member states, the process can be relatively quick. For example, the process from submitting a membership application to joining the EU for Finland was three years from 1992 to 1995.

Further details of how the EU accession process works are provided in the House of Commons Library briefing paper, EU enlargement: Ukraine, the Western Balkans and the accession process

Potential EU reaction to a UK membership application

Some commentaries have discussed the potential EU reaction if the UK were to seek to join the EU, suggesting that some Member States may be reluctant to agree to a UK return to the EU. Reasons for this include a concern that the membership issue would remain a point of contention between political parties in the UK and that a future UK government might seek to take the UK out of the EU again.

Among opposition parties, the Conservative party and Reform party oppose the UK joining the EU. The Conservative Party manifesto for the 2024 general election (PDF) emphasised the importance of the UK’s “post-Brexit freedoms”. The Conservatives have subsequently said they would oppose new UK-EU agreements that involve an obligation for the UK to align with EU laws or give jurisdiction to the Court of Justice of the EU, and that a future Conservative government would not be bound by a “bad Labour deal”.

The Reform party 2024 manifesto referred to the need to “grasp the huge opportunities of Brexit” and called for the scrapping of remaining EU-derived legislation in the UK (laws adopted through EU membership obligations that were assimilated into UK domestic law following Brexit), and the partial abandonment or renegotiation of the post-Brexit UK-EU treaties.

The Liberal Democrats manifesto for the 2024 general election (PDF) proposed a staged approach to rebuilding the UK’s relationship with the EU, with the eventual objective of the UK rejoining the EU single market. The Liberal Democrats have subsequently proposed the negotiation of a new UK-EU customs union.

The Green Party of England and Wales is in favour of the UK rejoining the EU “as soon as the political will is present”. The Scottish National Party advocates for an independent Scotland joining the EU.

UK opt-outs

Commentaries have also observed that if the UK applied to join the EU, the UK would no longer be guaranteed the opt-outs and special arrangements it had previously as an EU member state. These include the opt-out that the UK had from adopting the euro, from provisions establishing the Schengen border-free area in EU law and other common provisions on justice and home affairs policy and its rebate from the EU budget.

The EU has referred to the need for new states joining the EU to commit to the adopting the single currency when they have met the criteria to do so. However, while one member state (Denmark) has an explicit opt-out from joining the single currency, other member states have also indicated that they do not intend to adopt the euro or have not taken the steps needed to meet criteria for joining.

The opt-out on provisions relating to the establishment of the Schengen area and other justice and home affairs provisions also to apply to Ireland, and these relate to the retention by the UK and Ireland of a separate common travel area.

Rebates on financial contributions to the EU budget also continue to be in place for some EU member states.