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What is the British party system?

Political scientists see parties as forming a party system.

This is defined by the number and size of significant parties and the patterns of competition between parties.

There is no clear definition of how we decide whether a party is significant but the size of its national vote and the number of MPs that it has are the important factors. Thus, the UK Independence Party and the Green Party became significant with 3m and 1m votes respectively in the 2015 general election, even though they only had 1 MP each in Parliament. On the other hand, although Respect had 1 seat in Parliament before 2015, they only stood in few constituencies and their national vote was very small and so they could not be seen as a significant party.

The best known classification of party systems is that of Sartori:-


  • Dominant party systems where one party is normally returned to power in elections as with the Liberal Party in Japan.
  • Two party systems where two large parties compete against each other and alternate in power as with the Republicans and Democrats in the United States.
  • Multi party systems where there are several significant parties. Sartori argued that there were two types of these:-

a)     Moderate pluralism where most parties competed for the middle ground of politics and some or most of these formed stable coalition governments, for example in the Netherlands where the Christian Democrat, Liberal and Labour parties are in government together in different combinations.

b)     Polarised pluralism where large parties developed as anti-system parties, hostile to the current democratic system, and with such big ideological differences that it becomes difficult to form stable governments.  The classic example is Germany before the Nazi take over when the Nazi and Communist parties both had a large vote and it was difficult for centrist parties to govern.

What sort is the British party system?

From 1931 until 1974 Britain could be seen as having a two party system with the Conservative and Labour parties receiving over 85% of the votes in each general election and alternating in government.

From the February 1974 general election, when the Liberal Party received 19% of the vote and the two main parties’ share of the vote fell to 75%, Britain could be said to have what political scientists have called a two and a half party system.

The Liberals became significant as their success in gaining votes from the other two parties could decide which won the general election and, in 1974 and, again, in 1977, when neither party had a majority in Parliament the Liberals decided who formed the Government.

This two and a half party system continued to the 2005 and 2010 general elections when the Liberal Democrat share of the vote was 22-23% and the two main parties’ share fell further to 65-67% and this helped to bring the Liberal Democrats into Government after 2010.

In Scotland and Wales the systems became close to multi-party with the rise in the SNP and Plaid Cymru vote. Northern Ireland developed an entirely different party system with none of the British parties competing there.

With two Catholic and two Protestant parties and the ideological distance between them large it could be seen to be a polarised multi-party system. This is why the system for running the Northern Irish Government forces the two groups to cooperate across the sectarian divide.

In the run up to the 2015 general election Britain appeared to be developing a multi-party system.

In some opinion polls UKIP were getting up to about 20% of the vote and the Greens up to about 8% of the vote.

In the end, the First Past the Post system meant that, although both parties polled well, this was not translated into MPs.

The election also saw the collapse of the Liberal Democrat vote from 6m to 2m and they were left with only 8 MPs.

In contrast the SNP won all but three sets in Scotland.

There are now different party systems in each part of the UK:-

        In England we are closer to a two party system again though there are elements of a multi-party system and whether this becomes established depends on the future success of  minor parties

        In Scotland we have a dominant party system with the SNP here to stay.

        There is moderate pluralism in Wales, although Labour remains the largest party, with the Conservatives, Plaid Cymru and Labour competing for votes.

        There is still polarised pluralism in Northern Ireland with the Catholic/Protestant divide still very important.