Will extremist parties get more representation under AV or FPTP?

This week saw a spat between the YES and NO campaigns over whether AV or First Past the Post (FPTP) will lead to more representation in parliament for extremist parties, such as the BNP.

'Yes to fairer votes' says: "First Past the Post offers no protection against extremism. In town halls across Britain BNP councillors have won power opposed by the vast majority of mainstream voters. It's the same trick they hope to repeat at Westminster, perhaps explaining their support for a 'No' vote… Anything's possible when you only need 3 out of 10 voters on your side."

Baroness Warsi in the Sun: "This means AV could see candidates pandering to extremist voters - because to win a seat they will need to win the support of people whose first choices have already been eliminated. It could have serious repercussions in constituencies where the BNP vote is bigger than normal."

No to AV: "Not a single constituency has been identified as likely to fall to a small party under AV. One study in Wales suggests Plaid Cymru could even be wiped out, losing all 3 of its current seats. As Professor K.D. Ewing and Dr. Graeme Orr found, "a small party is unlikely to win any seats under AV."

No to AV: "While we hope that AV wouldn't lead to extremist parties winning win seats, it would certainly give them more influence — BNP second preferences alone could swing at least 35 seats. Moreover, they will gain legitimacy from a greater vote total. Fringe parties could expect their first preference vote to be higher than it is now, giving them more support and legitimacy. And mainstream politicians would pander to the extremists to try and win their second preferences."

Facts

Extremist parties, such as the BNP, are very unlikely to gain representation in Westminster under AV or FPTP. The lack of main stream support for extremist parties, and their lack of majority support in any constituency size electoral areas prevent them from gaining representation.

Left Foot Forward, a left-wing political blog, wrote an article that explains this issue further, laying out the conditions that would need to apply for a party like the BNP to gain representation in Westminster. It says: "They [the BNP] would need to have more votes than the winning margin (which is very rare); their voters would need to express a mainstream second preference (which is unlikely in most cases), and even where they do, those preferences would need to break very unevenly for one major candidate over another to have the potential to be decisive (and there is no evidence that they would do so)... The electoral geography of BNP support — strongest in heartland Labour seats — makes their ability to affect results even less plausible."

The article also argue that: "Pandering to BNP votes would prove a self-defeating strategy under AV. The winning candidate needs to seek 50% of the vote — since the BNP have under 2% of the vote and 80% of voters very strongly disapprove of them, any association with them is going to be toxic."

The House of Commons Briefing Paper also argues this point, saying that: "[AV] more accurately reflects public opinion of extremist parties, who are unlikely to gain many second-preference votes."