A proportional electoral system is more likely to return seats for smaller parties. Amongst these smaller parties, it is likely that we will find parties on either extreme of the left-right spectrum. The British National Party campaigned for PR for this reason (Channel 4 Fact Check, ‘Would AV help or hinder the BNP?’). Potentially even more extreme parties, such as the English Defence League, could get members of parliament under some proportional systems. It is not beneficial to the country to have extremist groups like this in parliament.