Explain three disadvantages of proportional representation

Voters and there representatives are not well connected to each other. In first past the post systems, which allow representation to represent a relatively small geographic area, there is a strong connection between representitives (ie. MPs in the UK) and voters (their constituents). For example if a large number of constituents vote for it, an area can call a by-election. This sort of connection is not prevalent in proportional representation systems. 

Proportional representation will lead to a legitimisation and increased power of extreamist and radical parties who do not act in the interests of society as a whole. For example, the extremist and highly unhelpful views of the BNP are limited to their own rallies and propaganda, the BNP is not legitimised by representation in parliament. The metioric rise of the Nazi Party in Germany can be attributed to the use of a proportional representation system which allowed Adolf Hitler to gain a voice in and legitimisation within the Weimar regime. That kind of democratic system did not lead to a good outcome. 

PR also leads to the excessive power of party elites to control and manipulate the political agenda. A candidates success depend on the party lists and thus a candidates success depends upon their ability to curry favour with party officials which will allow them to achieve their dreams of public office.