Electoral Systems

In the UK, it appears that at one point or another there's always an important election occurring. Whether that be a by-election for who should replace a previous MP or a general election to decide what party will be in power. If you are already 18 you may even have participated in an election already, but what do we actually know about electoral systems and what different kinds of electoral systems do we have in the UK? Let's take a look into electoral systems in this article.

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Table of contents

    UK electoral system

    An electoral system can loosely be defined as a set of rules that govern the way in which elections are conducted and how the results are interpreted.

    In the UK, electoral systems play an integral part in upholding democracy and democratic values. A principal function of the electoral systems is to provide representation.

    The purpose of the electoral systems used in the UK is to translate the votes cast by the electorate into seats represented in the elected chamber of the UK legislature, the House of Commons.

    Aside from representation, electoral systems also aim to promote accountability, encourage political participation, allowing the public to choose their elected government and experience a degree of influence over policies (by voting for those who propose policies they support).

    Alongside the House of Commons in Westminster, there is also the Scottish parliament, the National Assembly for Wales and the Northern Ireland Assembly. Electoral systems are the way in which members are elected to positions in these legislative bodies. The electoral systems used in the different Parliaments and Assemblies across the UK differ to some degree, and therefore there are four types of electoral systems that we witness across the UK.

    Electoral Systems Ballot Box StudySmarterFig. 1 Ballot Box

    Types of electoral systems

    The main types of electoral systems are either majoritarian, pluralist, proportional or mixed electoral systems.

    Plurality electoral systems are electoral systems where the elected representative is the candidate that receives the most votes. However, this does not mean this candidate received the majority of the votes.

    In the UK, this is seen in the First-Past-the-Post system.

    Majoritarian electoral systems are electoral systems in which there is a majority required to win (unlike with plurality systems), so essentially the individual elected receives over half of the votes. Depending on where majoritarian elections are being used, there are different types of majorities required in order to win an election.

    In the UK, the use of a majoritarian electoral system can be viewed in the Supplementary Voting System (SV) where a simple/working majority is required.

    Proportional representation electoral systems are electoral systems in which the votes a party receives are used to allocate seats proportionally. Therefore, if a party receives 20% of the votes in an election, they are allocated 20% of the available seats in government.

    In the UK, the use of the Single Transferable Vote (STV) is an example of proportional representation.

    Mixed electoral systems are electoral systems that use a mixture of the aforementioned electoral systems (majoritarian, proportional, and plurality systems) to determine election outcomes.

    In the UK, this is seen through the use of the Additional Members Systems (AMS).

    In theory in a system with proportional representation 20% of votes equals 20% of the seats. However, in practice it is usually not 100% proportional in this way and how close those two numbers are depends on the electoral system.

    First Past The Post (FPTP)

    First-Past-the-Post, usually abbreviated to FPTP, is the system that is used to elect Members of Parliament to the House of Commons in a general election. Aside from general elections, local elections also use FPTP across England and Wales.

    In the UK there are 650 Constituencies, during a general election candidates run to become the MP for particular constituencies. The candidate that gets the most number of votes becomes the MP for that constituency, which gives their party and the MP a seat in the House of Commons as a representative for that constituency. A party needs 326 seats to have a majority in the Houses of Commons and form a government.

    FPTP is also referred to as 'winner takes all' as the candidate needs only as little as one more vote than the other candidates to become MP. First-Past-the-Post often creates safe seats and marginal seats.

    For more details, check out these articles: Safe Seat and Marginal Seat.

    Safe seats are seats that have historically been won by a single party and often by a large margin, meaning the party who wins doesn't often change. While marginal seats are seats that are won by only a tiny margin of vote, usually 10% or less, and change hands often.

    Advantages and disadvantages of electoral systems- FPTP

    FPTP is a straightforward voting systems which makes it easy for voters to understand, it also produces a clear outcome with little ambiguity over results. The question whether the voting system should be reformed is a popular one, particularly among those who analyse electoral systems within in the UK, but fundamentally the use of FPTP has public support.

    Electoral Systems Protestors calling for proportional representation over first past the post StudySmarterFig. 2 Protestors calling for proportional representation

    A referendum was held in 2011 where the public were able to vote on whether there should be reform to the election system regarding the use of FPTP. The outcome of the referendum was that there was, in fact, public support for FPTP and no reform was desired at present. The turnout for his referendum was however incredibly low, and therefore questions surrounding reform still persist.

    The disadvantages of the FPTP system are that candidates are not required to have a majority to win, and it really only favours the largest parties, which has served to create a two-party system. It appears that in the UK, despite the existence of other political parties, the general election will almost always be a matter of whether the Labour Party or the Conservative party will be in power.

    For your exams you may be required to compare FPTP to a different electoral system, so it is important you know all four of the electoral systems mentioned in this article alongside their advantages and disadvantages!

    SV Electoral System

    Electoral Systems Sadiq Khan current Mayor of London StudySmarterFig. 3 Sadiq Khan, current Mayor of London

    The Supplementary Vote (SV) is a majoritarian system which is used to elect mayors and police commissioners. It is useful and straightforward to use when electing a singular person as opposed to a party.

    In the SV systems, voters select a first and second preference (the second preference is optional). If a candidate wins a majority of the first preference they are elected, however, if no candidate wins the first preference majority then all the candidates bar the top two candidates are removed from the vote. The second preference votes cast for the removed candidates are then added to the votes the top two candidates received in order to decide on the winner.

    This ensures the winner receives a majority (more over 50% of the vote) and is therefore the winner.

    Advantages and disadvantages of electoral systems- SV

    Arguments for the advantages of this system are that if used in wider electoral systems such as general elections the voter would be given the ability to vote for smaller parties yet still contribute to decided which of the two bigger parties will win, and as the winner requires a majority the system encourages candidates to achieve a wider array of support unlike FPTP.

    SV is however not a proportional system and instead of electing the most popular candidates it elects the least unpopular.

    STV Electoral System

    The Single Transferable Vote (STV) is used in the Northern Ireland Parliament and local elections in Scotland. STV is used within multi-member constituencies, (constituencies where more than one person is to be elected).

    In STV systems, voters rank the candidates in order of preference. There is a certain number of votes that are to be achieved if a candidate is to be elected. If first preference candidates meet this quota they are elected and any extra votes above the quota are transferred to the second preference candidate who is elected when they meet the quota. If no candidates meet the quota, the candidate with the fewest votes is taken out of the race and their votes are transferred to whoever is left in order of preference.

    Advantages and disadvantages of electoral systems- STV

    STV produces proportional outcomes and provides a wider array of choice for voters. The use of STV, which is a proportional electoral system also usually produces a government in which the parties present gained a majority of the vote.

    However, STV creates weak bonds between the elected representatives and constituents, and the general electoral process is slow and complicated to understand for the wider public.

    Additional Member System

    Electoral Systems 2021 Scottish Parliament Map using  the AMS StudySmarterFig. 4 2021 Scottish Parliament Map using the AMS

    The Additional Member System (AMS) is a mixed electoral system that uses both FPTP and proportional representation. AMS is used in the Welsh Assembly, the Scottish Parliament, and the Greater London Assembly. A number of parliamentary seats are allocated through the use of FPTP alone.

    For example, in Scotland, 73 of the 129 available constituency seats are allocated using FPTP and the remaining 56 are allocated through proportional representation.

    Voters have two votes, one for the candidate they want to represent their constituency and the second vote for a party. Each party produces a closed list of candidates, where candidates within their party are ranked in order. Seats will then be allocated to candidates within a party in order of their ranking on the 'party list'.

    Advantages and disadvantages of electoral systems- AMS

    In order to determine how many additional seats will be allocated, proportionately those on the party, using a formula. This allocation of additional seats can serve to boost the number of seats that parties that may of have done well in the FPTP voting will receive. This makes the election results more proportional and AMS is viewed as giving voters the best of both worlds through the use of FPTP and proportional system as well as providing voters with more choice. This is because voters can vote for a constituency representative from a particular party and cast a regional party vote for a different party.

    The disadvantages of the AMS is that some of the candidates elected do not have constituency responsibilities as they are allocated based on the party list whereas the candidates elected through FPTP do, so it creates two different types of representatives. The use of the party list also places too much power in the hands of parties, as they determine who is on the list and who gets left off.

    A method called 'zipping' is often used to increase gender representation when creating a party list. This is when the party list alternates between male and female representatives. So first on the party list may be a woman then a man then a woman and so forth.

    Electoral Systems - Key takeaways

    • The purpose of the electoral systems used in the UK is to translate the votes cast by the population into seats within government.
    • The main types of electoral systems in are majoritarian, pluralist, proportion or mixed electoral systems.
    • First Past The Post is the system that is used in Westminster parliament (House of Commons)
    • The Supplementary Vote (SV) is a straightforward majoritarian system which is used to elect mayors and police commissioners, where voters order their preference.
    • The Single Transferable Vote (STV) is used in the Northern Ireland Parliament and local elections in Scotland.
    • The Additional Member System (AMS) is a mixed electoral system that uses FPTP and proportional representation.


    1. Fig. 1 Ballotbox325CSCVL (https://commons.wikimedia.org/wiki/File:Ballotbox325CSCVL.png) by 325CSCVL (https://commons.wikimedia.org/w/index.php?title=User:%E7%AD%86%E5%92%8C%E6%93%A6%E8%86%A0%E5%BF%85%E6%9C%89%E7%94%A8&action=edit&redlink=1) licensed by CC-BY-SA-4.0 (https://creativecommons.org/licenses/by-sa/4.0/deed.en)
    2. Fig. 2 Make Votes Matter ! No to FPTP. Yes to PR. (https://commons.wikimedia.org/wiki/File:Make_Votes_Matter_!_No_to_FPTP._Yes_to_PR._(51868539320).jpg) by Alisdare Hickson (https://www.flickr.com/people/59952459@N08) licensed by CC-BY-SA-2.0, (https://commons.wikimedia.org/wiki/Category:CC-BY-SA-2.0)
    3. Fig. 3 Sadiq Khan 2020 (https://commons.wikimedia.org/wiki/File:Sadiq_Khan_2020.png) by Chabad Lubavitch licensed by CC-BY-2.0 (https://commons.wikimedia.org/wiki/Category:CC-BY-2.0)
    4. Fig. 4 Scottish Parliament election map 2021 (https://commons.wikimedia.org/wiki/File:Scottish_Parliament_election_map_2021.svg) by DrRandom Factor (https://commons.wikimedia.org/wiki/User:DrRandomFactor) licensed by CC-BY-SA-4.0 (https://commons.wikimedia.org/wiki/Category:CC-BY-SA-4.0)
    Frequently Asked Questions about Electoral Systems

    What are the different types of electoral system?

    There are majoritarian electoral systems, proportional electoral systems, plurality electoral systems and mixed electoral systems. 

    What is the UK electoral system?

    In the UK  first pass the post is most widely used in UK electoral systems, though there is also the use of the additional member system, the single transferable vote and the supplementary vote depending on the election in question.

    What is an electoral system?

    An electoral system is a method used to translate votes cast into governmental seats. 

    Test your knowledge with multiple choice flashcards

    What is the aim of electoral systems in the UK?

    Which electoral system is used for mayoral candidates?

    Which of the following is an advantage of First Past The Post?


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