The UN Charter establishes the membership of the Security Council. The following information is from the UN Membership research guide:

Permanent Members

According to Oppenheim's International Law : United Nations, "Permanent membership in the Security Council was granted to five states based on their importance in the aftermath of World War II." Sometimes referred to as the P5, the permanent members of the Security Council have a unique role that has evolved over time.

UN Research Resources on the P5:

• Repertoire of the Practice of the Security Council
• Repertory of Practice of UN Organs
• Veto data from the UN Peace & Security Data Hub

Non-permanent Members

The membership of the Security Council is one of the most debated aspects of the United Nations. The matter of non-permanent membership has been discussed continually since 1945. In addition to discussions during the drafting of the Charter, the topic has been raised both in and out of formal UN meetings, in informal forums and scholarly articles. The question of the composition of the Security Council has been examined both within the UN in various bodies and by outside organizations, scholars and researchers. Over time, there have been many proposals and positions put forward.

Membership of Security Council

• Security Council website members database provides states elected and membership by year
• UN Member States on the Record has information on when a country was a member of the Security Council, among other things

Equitable Geographic Representation

The question of how to apportion the available seats among regional groups has been debated repeatedly. In 1953 when the General Assembly met to elect non-permanent members to the Security Council, the delegate of the USSR referred to an oral "gentleman’s agreement" about the number of seats to be accorded various regions (A/PV.450). Until the amendment of the Charter in accordance with A/RES/1991 (XVIII), there was no formally prescribed number of seats for any region. 

From 1994-2009, the Open-ended Working Group on the Question of Equitable Representation on and Increase in the Membership of the Security Council and Other Matters related to the Security Council was the main UN body charged with discussing this matter. The reports of the Working Group provide an overview of their proposals, discussions and recommendations. The following information about the Working Group is from the UN Charter research guide:

Additional proposals:

• A/59/565: Note transmitting A more secure world : our shared responsibility : report of the High-level Panel on Threats, Challenges and Change
• A/59/L.64: Security Council reform : draft resolution ; also known as the Group of 4 proposal for the initial sponsors of the draft resolution: Japan, Brazil, Germany, India

UN Research Resources on Equitable Representation

• Repertoire of the Practice of the Security Council
• Repertory of Practice of UN Organs

Research Suggestions

There are many ways to approach research on this topic.

One way is to begin with a general internet search to find positions by think tanks, NGOs or organizations. Much has been published online. Keep in mind general principles of research and carefully evaluate the perspective or opinion of the author and the quality and source of the information provided. 

Another way is to begin with secondary resources such as books and articles, including scholarly sources on the United Nations. These resources often cite relevant UN documents, which can then be found in the UN Digital Library or other sources. The Resource pages of the research guides on the Security Council and the UN Charter can provide some starting points for research on secondary sources.

Another approach is to look directly into UN documents such as meeting records, letters and reports. With this approach, keep in mind that the General Assembly determines the composition of the Security Council and is the main organ where debate on this topic has happened. The Repertory of Practice of United Nations Organs contains detailed studies on Article 23 about the practice of the General Assembly in relation to the elections to the Security Council. This topic may be raised in the General Assembly in relation to several agenda items which have changed over time, including the question of equitable representation on and increase in the membership of the Security Council and other matters related to the Security Council, UN reform, and Charter amendment. States have also made statements on this matter during the general debate.