Technically in the UK we have a multiparty system, however two parties dominate the political establishment: the Conservative Party and the Labour Party. These two parties have fought over power since the end of the second world war. A two-party system is a system where two major political parties dominate politics within a government. One of the two parties typically holds a majority in the legislature and is usually referred to as the majority party while the other is the minority party. Whereas a multiparty system is a system in which multiple political parties have the capacity to gain control of government offices, separately or in coalition. The UK has factors of both a multiparty system and a two party system. .
For the past eight decades either Labour or Conservative have lead Parliament, in this sense we are a two party system because only two parties have been in power for such a long time. Labour and Conservative are also the only two parties who are big enough to run the country, due to the amount of support these two parties have gained over the years, people have realised that voting against them would not change the outcome of the vote due to the spoiler effect. Even when a smaller party with a similar ideology to one of the parties comes along they will merely take away votes from the larger party leaving the other one with the most votes. This can both indicate to us that the UK has multi-party system, and a two party system; because only two parties will still ever get into Government, but there is the possibility for smaller parties to be established. .
An example of the UK having a multiparty system is the voting system that the UK has – in the UK we have a first past the system, which shows more than the two main parties, which makes it clear that there are more than two parties in the UK – therefore a multi-party system, however first past the post doesn't give enough representation to the smaller parties.