The authoritative source for independent research on UK-EU relations

The UK continues to interact with the EU and with individual member states following its departure from the EU, but neither how the EU handles these relations nor the constraints that apply to bilateral texts that member state governments have concluded with the UK is well understood.

This explainer sets out how the UK-EU relationship is structured, how decisions are taken on the EU side, and the respective roles and responsibilities of EU institutions and EU member states. It also discusses how the bilateral accords that the UK has signed with a number of national governments fit alongside the Withdrawal Agreement, the Trade and Cooperation Agreement, and the obligations of those governments to the EU.

What is the basis of the UK’s relationship with the EU?

The formal relationship is governed by two treaties: the Withdrawal Agreement (WA), which covers citizens’ rights and the UK’s financial obligations arising from its period of membership, and includes the Windsor Framework on Northern Ireland; and the Trade and Cooperation Agreement (TCA), which regulates the trade relationship between the UK and the EU.

Where does interaction between the EU and the UK take place?

Each Agreement creates a committee structure to oversee the implementation of its provisions, as well as to resolve disputes. Committees are co-chaired by the UK and the EU and bring together representatives of the two sides.

The WA has a system of Specialised Committees, headed by a Joint Committee. In the case of Northern Ireland, there is also a Joint Consultative Working Group, as well as sub-groups with more specific responsibilities (e.g. goods, the Single Electricity Market).

The TCA has eight Specialised Committees and ten Trade Specialised Committees. The Joint Partnership Council is the top body. The TCA provides for technical working groups and for the possibility of creating more working groups as cooperation deepens, as well as for the possibility of extending the scope of the agreement through supplementing agreements.

The TCA also establishes an EU-UK Parliamentary Partnership Assembly (PPA), with representatives from the European Parliament and the UK Parliament. The PPA is informed of the decisions and recommendations of the Partnership Council and can make recommendations to the TCA Partnership Council, as it has done on energy cooperation and the EU-UK common effort to support Ukraine. The PPA also has the power to request information on the implementation of the TCA.

In addition, the TCA provides for each side to set up a Domestic Advisory Group (DAG), made up of organizations representing industry, businesses, trade unions and the third sector. The UK and EU DAG participate and feed their discussions into the annual Civil Society Forum, which was created under the TCA and is co-chaired by representatives from the EU Commission and the UK Foreign Office. On the EU side, the DAG advises the Commission on the implementation of the TCA.

Who has responsibility for what on the EU side?

Procedures governing participation and representation in the committee systems on the EU side are set out in decisions adopted by the Council of the European Union concerning the WA and the TCA respectively. While the Council establishes the positions to be taken on the Union’s behalf, the Commission represents the EU, states the EU’s position in the committees, and reports back to the Council. Member states are permitted to send one representative each to meetings of the Partnership Council and of other joint bodies established under the TCA. When bodies in either the WA or TCA committee system are called upon to adopt acts with legal effect, the Commission submits recommendations to the Council, which authorises the opening of negotiations, and when an agreement is reached, the Council authorises its signing. The European Parliament is kept informed by the European Commission services of such acts. In the case of a dispute between the UK and the EU over areas covered in the TCA and the WA, the Commission represents the EU in arbitration tribunals.

The European Parliament’s United Kingdom Contact Group, which oversees both Agreements, is the EP’s main point of contact with the European Commission. Composed of Members of the European Parliament (MEPs), the UKCG is co-chaired by the chair of the European Parliament’s Delegation to the EU-UK Parliamentary Partnership Assembly (D-UK), and the chairs of the Committee on Foreign Affairs (AFET) and Committee on International Trade (INTA) in the European Parliament.

The European External Action Service (EEAS), the body responsible for the EU’s diplomatic relations, also has a role. The Delegation of the European Union to the UK monitors the implementation of the two agreements, and convenes regular meetings of member state diplomatic missions in London. It is also an interlocutor for UK decision-makers in Whitehall and across the devolved administrations and provides a point of contact for businesses and citizens.

In Brussels, a UK unit inside the EEAS oversees the implementation of UK-EU ‘regular dialogues’ on cybersecurity and counter-terrorism under the TCA.

While the Court of Justice of the European Union (CJEU) plays no part in the governance of the TCA, the WA allows UK courts to ask preliminary questions to the CJEU on the interpretation of the provisions of the WA regarding citizens until 31 December 2028 and infringement cases against the UK to be brought before the Court until 31 December 2024.

Since some EU rules on goods apply to Northern Ireland, the Court is the final arbiter of EU law for any dispute over their application.

How are responsibilities shared within each institution?

In the Commission, Executive Vice-President Maroš Šefčovič, or one of the EU’s alternate co-chairs, represents the EU in the WA Joint Committee. Maroš Šefčovič also represents the EU in the TCA Partnership Council. The Secretariat General, the Commission’s central coordinating body, which supports and oversees the work of the Commission departments, provides advice, monitors, and manages the Commission’s input into the bodies of the TCA and the WA. The Secretariat General also co-chairs the Specialised Committees on the Windsor Framework and on citizens’ rights. Other Specialised Committees under the WA are co-chaired by the relevant Commission Directorate General.

Commission Directorates General also co-chair the work of the Specialised Committees and Trade Specialised Committees under the TCA in line with their sectoral responsibilities. For instance, the Directorate General for Trade is directly involved in nine of the Trade Specialised Committees and co-chairs the Civil Society Forum which brings together the UK and EU Domestic Advisory Groups (DAGs) once a year.

In the Council, the Working Party on the UK assists the Committee of Permanent Representatives (COREPER), composed of the heads or deputy heads of the member states’  missions to the EU, and ministers on matters related to the EU-UK relationship. It reviews decisions taken by the Partnership Council and the Joint Committee and considers legislative proposals. The Working Party is chaired by the six-monthly presidency of the Council and meets frequently, often more than once a week. It provides the main locus for reporting and sharing information between member states and the Commission on interaction with the UK, beyond the formal agreements of the TCA and the WA, including foreign policy and multilateral relations, and bilateral contacts. The Working Group is supported by the EU-UK Team in the Council Secretariat’s Directorate-General for General and Institutional Policy (GIP).

Are the committees and sub-committees the only channels for interaction between the EU and the UK?

No. The UK and EU can cooperate in other areas. For instance, the recently established Joint EU-UK Financial Regulatory Forum, which follows the adoption of a Memorandum of Understanding between the UK and the EU for regulatory cooperation on financial services in June 2023, sits outside the Committee structures of the TCA. The EU is represented by the relevant Commissioner and Directorate General in charge of financial services regulation. In other areas not covered by the TCA, such as sanctions following the Russian invasion of Ukraine, cooperation can be more ad hoc. Another example is the ‘Calais Groupe’, which brings together ministers from the UK, France, Germany, Belgium and The Netherlands, and representatives from the European Commission, to discuss irregular migration.

At the very top, the UK Prime Minister regularly holds bilateral meetings with the President of the European Commission on the fringe of multilateral international summits, although there is no regular UK-EU political summit.

What about bilateral cooperation between the UK and individual member states?

The UK can sign bilateral agreements with individual member states, but they are limited in scope and, for the most part, non-binding. EU member states must comply with EU law, are obliged to ‘inform the Commission in due time of their intentions and of the progress of the negotiations’, and cannot enter into agreements where the EU has exclusive competence or in areas covered by the WA or the TCA unless specifically authorised. Any text must be compatible with the relevant Agreement and with EU law. In those areas where the TCA allows member states to conclude bilateral agreements with the UK  (air transport, administrative cooperation in the areas of customs, VAT and social security), any such agreement must also ‘take into account the internal market and broader EU interests.’

Whilst the UK has signed some bilateral agreements with EU member states that are binding in very specific areas, such as on the protection of classified information, most of the declarations with EU member states on bilateral cooperation are non-binding and do not give rise to any obligations under international or domestic law. They are broad, but mainly aspirational. Whilst reaffirming a commitment to multilateral cooperation, they usually cover bilateral relations in foreign policy, security and defence, economic cooperation, law enforcement and judicial cooperation, people-to-people links (mobility), environment and energy, and research and science.


Reflecting the UK’s proximity and importance, the EU has developed a unique set of institutional arrangements to manage its relationship and ensure a flow of information between EU institutions and national capitals. The outcome is a detailed organizational structure that aims to ensure the smooth day-to-day implementation of the Agreements. It provides clear procedures for ensuring transparency and communication, and processes through which future cooperation can be built.

By Professor Hussein Kassim, Senior Fellow, UK in a Changing Europe, and Dr Cleo Davies, Senior Research Fellow, University of Warwick. 


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