It's not hard to believe that the BNP, like all small parties, could expect a higher vote under AV. Someone tempted to vote BNP now may resist doing so in favour of choosing between the top two candidates in his or her constituency. Under AV they need have no hesitation voting BNP number one and then transferring their vote to a more respectable party. Having two or three bites of the cherry is a luxury AV affords the supporters of extremist parties, but not the supporters of mainstream parties.What I'd like people like Joan Ryan to explain is why the people who support the BNP shouldn't have some say in the formation of government. Surely democracy is about getting a parliament that represents them best, and if that means that people who like what the BNP are about get some sort of say in how the country gets governed?
This does not mean the BNP would be any more likely to win a seat in the Commons under AV than it does now. But it would make the party more influential. The major parties would want to win transfers from people backing the BNP. It's not hard to imagine how ugly that would be.
Note: Joan Ryan was the third highest claiming MP who also flipped her home and voted to keep her expenses secret. Under an AV system, a lot more of those MPs would have found themselves being destroyed at the ballot box by alternative candidates.