Petits partis

http://www.palgrave-journals.com/bp/journal/v3/n2/full/bp20085a.html

Electoral system
Small parties find it difficult to break into the British plurality voting electoral system because most individual constituency contests are dominated by the major parties. In general elections, people are especially unwilling to ‘waste’ their votes on a party with little chance of winning a seat. Where a small party can concentrate its vote geographically, as with the Welsh and Scottish nationalists, it has a better chance of gaining representation, but the Greens have been unable to establish any similar regional base.
The significance of the electoral system is underlined by the impact of the introduction of proportional representation in second-order elections, which immediately saw the election of Greens to the European Parliament, the Scottish Parliament and the Greater London Assembly. Suddenly, the Green Party began securing the vote share of between 5 and 10% that has delivered electoral success to green parties elsewhere in Europe. Other factors may have contributed to these successes. Green parties across the EU have consistently performed better in European elections than in domestic contests, suggesting that voters may regard the environment as an issue that is best dealt with at a supranational level and that the presence of Green MEPs would therefore be desirable. More generally, second-order elections are often treated by the electorate as an opportunity to cast a protest vote for a small party against the government and other established parties, as illustrated by the Green success in the 1989 European Parliament election. It is impossible to disentangle these motivations from the impact of proportional representation, as the latter would probably have encouraged the former. Yet it is clear that the use of proportional representation in these contests greatly benefited the Greens.
Of course, as the Welsh Assembly demonstrates, the presence of proportional representation is no guarantee of green success. Elsewhere, both Norway and Denmark have electoral systems based on proportional representation and electorates with high levels of environmental consciousness and postmaterial values that might appear to provide ideal conditions for green parties to flourish, yet they have failed to do so.6 However, if the introduction of proportional representation for British general elections is not a sufficient condition for a significant Green breakthrough in the foreseeable future, it is probably a necessary one.7