Introduction – Enlargement

After six rounds of enlargement, the EU has expanded from a six-member entity into the world’s largest trading bloc with 27 member states and a population of 490 million.

In a little more than 30 years, the EU has grown from a six-member entity with a population of 185 million, to 15 members with 375 million, to 25 members with 455 million citizens in 2004, before becoming a 27-member bloc with roughly 490 million citizens on 1 January 2007. Meanwhile, 'widening' the club's membership has gone hand in hand with 'deepening' integration. 


Even some of the successful enlargement processes had to surmount numerous obstacles: the applications of the United Kingdom in March 1961 and 1967 were twice vetoed by France. Denmark, Ireland and Norway subsequently withdrew their applications. The four of them re-applied for the third time in 1969, and were all successful in negotiating their membership, but the Norwegians rejected the draft Accession Treaty in a referendum in September 1972. Iceland has never officially applied to become a full EU member.

Several membership applications have not led to enlargement: 

Country Application Membership
Founding members
Belgium 1957
France 1957
Germany 1957
Italy 1957
Luxembourg 1957
Netherlands 1957
First enlargement
Denmark August 1961 January 1973
Ireland July 1961 January 1973
United Kingdom August 1961 January 1973
Second enlargement
Greece June 1975 January 1981
Third enlargement
Portugal March 1977 January 1986
Spain July 1977 January 1986
East Germany German reunification October 1990
Fourth enlargement
Austria July 1989 January 1995
Finland March 1992 January 1995
Sweden July 1991 January 1995
Fifth enlargement
Cyprus July 1990 1 May 2004
Czech Republic January 1996 1 May 2004
Estonia December 1995 1 May 2004
Hungary March 1994 1 May 2004
Latvia October 1995 1 May 2004
Lithuania December 1995 1 May 2004
Malta July 1990 1 May 2004
Poland April 1994 1 May 2004
Slovakia June 1995 1 May 2004

June 1996

1 May 2004

Sixth enlargement 

Bulgaria December 1995 1 January 2007
Romania June 1995

1 January 2007

Next enlargements (planned)

Croatia 20 February 2003 1 January 2009 [scheduled]
Turkey 1963 uncertain
Former Yugoslav Republic of Macedonia 17 December 2005 uncertain
April 1962 
Accession rejected by referendum in September 1972 
July 1987 
Rejected by the Council as a non-European state 
June 1992 
Membership in the European Economic Area rejected by referendum in December 1992.
Application for membership subsequently withdrawn. 
December 1992 
Accession again rejected by referendum in November 1994. 


The Copenhagen Council of June 1993 laid down the foundations for the EU's fifth enlargement process. The Council declared the so-called 
Copenhagen criteria
, under which a candidate country must meet:

  • Political criteria - "stability of institutions guaranteeing democracy, the rule of law, human rights and the respect for and protection of minorities";
  • economic criteria - "the existence of a functioning market economy as well as the capacity to cope with competitive pressure and market forces within the Union", and; 
  • acquis criterion - "ability to take on the obligations of membership, including adherence to the aims of political, economic and monetary union".  

The Commission issues regular reports on candidates' progress in meeting the Copenhagen criteria. Progress is assessed for each criterion, as well as for each of the thirty-one chapters of the acquis. For the negotiations with Croatia and Turkey, the acquis was divided into 35 chapters.

A 'standard' accession process entails the following steps:

  • Application for membership is submitted;
  • the Commission formulates its opinions ['avis'] based on assessments against the Copenhagen criteria;
  • accession negotiations are opened and concluded based on Council resolutions;
  • accession treaty is ratified by the member states' parliaments/citizens, and; 
  • accession takes place.  

The applicant countries are judged against the same set of criteria and once a country qualifies as a 'candidate' for full membership status, the negotiations proceed according to a preset agenda.

The continuing enlargement of the EU is based on economic as well as security and identity-related considerations. Besides aiming to widen the European Single Market (thereby stimulating growth), member states are also expanding the Union to promote greater stability and enhance security. Meanwhile, under the Rome Treaty, the EU describes itself as an entity in which "any European state" may apply for membership. The EU's natural limits are understood to be the borders of Europe, but the definition of this boundary is unclear.

Especially accession negotiations with Turkey have stirred the debate on how far the EU should expand, or it's absorption capacity. According to the Commission 2006 Enlargement Strategy Paper, the EU's integration capacity is determined by three factors:

  • Institutional: "The Union needs to ensure that its institutions and decision-making processes remain effective and accountable, for the sake of current member states as well as in view of further enlargement"; 

  • EU policy impact: "The Union needs to be in a position, as it enlarges, to continue developing and implementing common policies in all areas. Assessment of the impact of enlargement on EU policies will take place at all key stages of the enlargement process.", and;  

  • EU budget: "Before any further accession, the EU will need to decide on the overall budgetary means required...The Commission's analysis will take account both of the budgetary aspects and of the increased economic dynamism generated by accessions." 


In its 2006 Enlargement Strategy Paper, the Commission underlines the principles of enlargement: consolidation, conditionality and communication. The EU executive has taken a more cautious approach on any new enlargement commitments - Commission President José Manuel Barroso and Enlargement Commissioner Olli Rehn have underlined the need to have an institutional settlement before any further enlargement takes place.

According to Christopher Preston (Enlargement and Integration in the European Union, London: Routledge, 1997), the EU's "classical method of enlargement" was based on a "constant pattern both in the formal accession procedured adopted, and in the implicit assumptions and principles which have shaped the expectations of the participants and the progress of negotiations". Preston identified six principles of the EU's "classical method":

  • Applicant countries must accept the acquis communautaire in full (no permanent opt-outs available);
  • accession negotiations focus exclusively on the practicalities of the applicants taking on the acquis;
  • the problems arising from the enlarging Community's increased diversity are addressed through the introduction of new policy instruments rather than by reforming the existing instruments;
  • new members are integrated into the Community's institutional structures on the basis of limited adaptation, with the promise of a fundamental review after enlargement;
  • the Community prefers to negotiate with closely related groups of states, and; 
  • existing member states pursue their own interests throughout the enlargement process and collectively externalise their internal problems.  

In his paper on the EU's enlargement methodology, Klaudijus Maniokas (Methodology of the EU Enlargement: a Critical Appraisal) argues that the EU's fifth enlargement (of May 2004) process was characterised by:

  • Increased complexity (more stages, more and improved controls to access);
  • differentiation (whole sets of conditions developed for each negotiating stage);
  • conditionality (conditions became more detailed and flexible throughout the process), and;
  • asymmetry (instruments based on contractual more or less mutual obligations were gradually replaced by instruments based on unilateral obligations).  
  • On 1 January 2007 Bulgaria and Romania joined the EU.
  • Croatia, Turkey and Macedonia were granted candidate status in 2005 and negotiations are ongoing.
  • The EU has given the countries of the Western Balkans the perspective of becoming EU members once they fulfil the necessary conditions.

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