This definition of party system refers to the typical structure of parties within a political system. It describes the normal number of parties that compete effectively. Thus we may speak of dominant, two-, three- or multi-party systems. It also refers to the typical party make-up of governments – for example, single-party government, coalitions and so on.

The party system in the UK has varied from two-party systems – where government swings back and forth between two parties such as Labour and Conservative with very little contribution from other parties (1945 – 1974) , to a ‘dominant’ party system, featuring long reigns in government by one party followed by the other (1979 – 2010).

It can be argued that today we have a multi-party system in the UK, as we have recently had the Liberal Democrats in a coalition government, the SNP have 56 seats, and UKIP received four million votes. However, others argue that as long as FPTP is the electoral system, there will always be more or less a two-party system.