FactCheck’s Twitter followers asked us for a round-up of the biggest claims made by the Yes to AV and No to AV camps.

With the referendum on May 5th, many said there are still too many smoke-and-mirror tactics to make an informed decision.

Here we check the claims you said were the most repeated, and most misunderstood.

YES TO AV CLAIMS:

1. Safe seats led to the expenses scandal

“There is even evidence of a link between how safe seats are and the expenses scandal revelations.” - Nick Clegg, The Daily Telegraph, April 21, 2011

The Political Studies Association found very little evidence that MPs were more likely to be implicated in the 2009 scandal over expenses if they occupied safer seats.

Meanwhile, the right-of-centre think tank Policy Exchange carried out a study looking at whether there was a link between MPs ordered to repay their expenses and the size of their majorities.

It found that length of service that was the key factor, not the size (and therefore safety) of the seat.

MPs elected in safe seats in 2001 or 2005 were no more likely than MPs elected in marginal seats in the same elections to claim dubious expenses.

What’s more, introducing AV wouldn’t call an end to safe seats. Seats with clear majorities under FPTP would likely remain that way under AV.

Some “fairly safe” seats could become less so under AV.  However, AV would also make some seats safer – Lib Dems for example, would benefit from second preferences.

2. AV won’t help the Lib Dems

Nick Clegg has “flatly” disagreed that AV is favoured by the Lib Dems because they would be the party most likely to benefit from the system. “It’s impossible to tell how millions of people across the country will vote when they’re given more choice.” – Nick Clegg, The Guardian, April 20, 2011

It seems futile to argue that a vote for the Yes camp wouldn’t vindicate Nick Clegg or the Lib Dems – it would be a victory for him and the Lib Dems because it was a condition of the coalition.

But as Ed Miliband has said: “We can’t reduce the second UK wide referendum in our political history to a verdict on one man.”

FactCheck agrees, so to the wider issue. Well, we can’t know for absolute certain how people will vote but academic modelling shows us that  AV “always boosts the Liberal Democrats”, the PSA says.

As a centrist party, the Lib Dems would pick up many second preferences. On that basis, the Lib Dems’ share of seats would be boosted somewhat, at the expense of the other main parties.

Ipsos-Mori concurs, adding that the “one thing that is pretty certain is that AV won’t always help Labour, or always help the Tories, under all circumstances. But it will probably always help the Lib Dems”.

3. MPs would need 50 per cent support

“Your next MP would have to aim to get more than 50 per cent of the vote to be sure of winning” - Yes to Fairer Votes

If a candidate gets more than 50 per cent in the first count, they are elected.

If no candidate gets more than 50 per cent, the least popular candidate is knocked out of the race. Voters who backed the eliminated candidate have their second choice put forward instead, alongside the first choice of voters’ whose candidates are still in the race. This process carries on until someone gets 50 per cent.

Mr Clegg is right that candidates will have to aim for 50 per cent of votes,  though it is true that some candidates will end up being elected on fewer than 50 per cent of all the votes cast.

The PSA explains that because voters do not have to rank all the candidates, some votes are likely to be “exhausted” (meaning that all the preferred candidates have been eliminated), before the end of the counting process.

4. AV was used to elect David Cameron as leader of the Tories

“It was used the Conservative Party leadership election. If it is good enough for the Conservative Party why don’t they think it is good enough for the rest of us?” - Nick Clegg,  BBC Breakfast, April 20, 2011

Northern Ireland currently uses AV for local government by-elections. In the United States, AV is called “instant run off” and it is used in some local elections.

In the UK, the Labour and Liberal Democrat parties use it for their leadership elections, and it is also used to elect the chairs of House of Commons select committees.

However, it is a close cousin of AV, the “multi-round system” that is used in the Conservative Party leadership elections.

As for national parliamentary elections, the only countries to use AV are Australia, Fiji and Papua New Guinea.

NO TO AV  CLAIMS:

1. AV will cost £250m

“The change to AV will cost up to an additional £250 million” - No to AV

Central to the No camp’s claim is that an AV system will need electronic voting machines, which would add £130m to the bill for an AV election. FactCheck previously proved this spurious.

There is no evidence that AV would require an electronic system. And as the Political Studies Association (PSA) points out, elections held under AV – and under the more demanding STV system – in Australia, Ireland and Scotland are all, in general, conducted using traditional paper ballots.

The AV referendum itself is estimated to cost £91m, regardless of the result. Subtract this £91m cost and the £130m from the No’s estimated £250m and you are left with a cost of £29m for voter education.

Aside from educating the voter, counting the votes would take longer than under FPTP. However, there are no estimates on how much this would cost.

The Cabinet Office has set aside £120m for the next general election; £10m more than the 2010 election (which cost £82m to run and £30m to deliver candidates’ election leaflets).

The PSA said: “Even if we suppose (unrealistically that the current cost of running an election (up to £90m) would be doubled by the introduction of AV, that implies an annual cost across a five-year electoral cycle of only around 30p per person. Clearly, this is a very small sum.”

Read more on our latest investigation: Clegg, Huhne and the £250m question – who’s right about the cost of AV?

2. Hung parliaments

“AV leads to more hung parliaments” – No to AV

AV would not lead to permanent hung parliaments and coalition governments.

The best academic research we have suggests that AV wouldn’t make big landslides a thing of the past, and nor would it make hung Parliaments more likely. However, changes in how people are voting mean coalitions are already becoming more likely under FPTP.

The British Election Study results shows that under AV – as with FPTP – only in 2010 would we definitely have seen a coalition in power.

The Institute for Public Policy Research (IPPR) concludes that hung Parliaments are indeed more likely in the future. But that will be the case under both AV and FPTP, and it reflects the long-term growing power of the Liberal Democrats more than any inherent feature of either voting system. For further analysis see previous FactCheck: Get used to more coalitions – just don’t blame it on AV.

3. AV will help the British National Party (BNP)

“It could have serious repercussions in constituencies where the BNP vote is bigger than normal.“ Baroness Warsi, The Sun, March 30, 2011

AV could boost the number of votes for the BNP but it would be highly unlikely to help the party win any seats.

In fact, in a very divided constituency, the BNP arguably has a better chance of winning a seat under First Past the Post than under AV.

Take Australia’s far-right One Nation party – in 1998 Pauline Hanson would have won a seat under FPTP but under AV she didn’t pick up enough low preferences from mainstream voters.

The secondary votes of BNP supporters also wouldn’t swing a seat for any other party on their own – going on last year’s results.

The only way the BNP would do better would be through a move to PR (proportional representation) – which would give them seats in proportion to the share of the vote they achieve – and that’s not on offer.

“AV is a retrograde step – it’s worse than what we’ve got now,” the BNP’s deputy chairman Simon Darby told FactCheck.

“We are never going to get our feet under the table under the AV system.”

For further analysis read previous FactCheck: Would AV help or hinder the BNP?

4. AV gives some people more votes than others

“FPTP sticks to the principle of ‘one person, one vote’ – unlike AV, where supporters of fringe parties can end up having their vote counted several times, while mainstream voters only get one say,” - No to AV.

AV does not give people extra votes. The system sticks to the principle of “one person, one vote”.

In the first round, everyone’s first preference is counted as one vote. To win the first round, a candidate has to achieve more than 50 per cent of all the votes.

If no one gets 50 per cent of the votes, the candidate with the fewest votes is eliminated. In the second round, if your favourite is still in the race your first preference still counts for one vote – but if your candidate was eliminated, your first preference now counts for zero and your second preference counts for one vote.

Every voter would be treated equally with each vote only counting once in deciding who is elected in each constituency.

By Emma Thelwell