3 May 2011 Last updated at 11:03

AV referendum: Best arguments for voting Yes or No

Britain decides on Thursday whether to change the way it elects MPs to the Westminster Parliament.

So what are the best arguments for keeping the current "first past the post system"? And the strongest reasons for changing to the alternative vote (AV), in which people can rank candidates in order of preference?

BBC News asked the two rival campaigns to come up with the top five reasons why you should back their cause in the referendum.

Here is what they said:

VOTE YES	VOTE NO
1. AV makes MPs work harder It can't be right or fair that with the current system MPs can get elected on fewer than three out of ten votes. The Alternative Vote raises the bar. All MPs would have to aim to get more than 50% of the vote, and so will have to work harder to win - and keep - our support. They'll have to speak to more voters and reach out to the wider community. That's bad news for complacent MPs - and extremists. 2. AV cuts safe seats While many of us have to worry about our jobs the old system means most politicians don't have to. Most seats are currently so "safe" that their incumbents don't have to worry about re-election. It's no wonder MPs seem remote and unresponsive when their elections are a foregone conclusion. AV reduces the number of safe seats - and "safe" MPs will have to up their game, because they will no longer be able to enjoy "jobs for life" with minority support. 3. AV is a simple upgrade When politics was a two-horse race in the 1950s the old system worked. But as voters have embraced more parties it's easier for MPs to get in with a handful of votes. AV keeps what is best about our current system - the link between an MP serving their local constituency - and improves on it. Your ballot paper is unchanged, hung parliaments are no more likely, but every MP will have to do more to secure majority support. It's a small but necessary change. 4. AV make votes count The old system has given MPs license to ignore millions of voters across the country. Parties and politicians just target the few swing voters they need to win, with the last election decided by fewer than 460,000 voters - just 1.6% of the electorate. AV means you will have more chance of deciding who speaks in your name in Westminster. Just rank the candidates 1,2,3… and you can show your support to anyone you think is up to the job. Then if your favourite candidate can't make it, you can still have a say. There's no longer any need to vote tactically, and more voters in more seats will help decide our elections. 5. AV is our one chance for change This is the first time we have been given a say on changing the way we do politics in this country. We may not get asked again. On Thursday the choice is simple: if you're happy with business as usual at Westminster, vote No. If you want to change politics for the better, vote Yes.	1. AV is unfair Under the AV system, some people would get their vote counted more times than others. For generations, elections in the UK have been based on the fundamental principle of 'one person, one vote'. AV would undermine all that by allowing the supporters of fringe parties to have their second, third or fourth choices counted - while supporters of the mainstream candidates would only get their vote counted once. 2. AV is not widely used AV is only used by three countries in the world - Fiji, Australia, and Papua New Guinea - and even they don't like it. In Australia, av hasn't made their MPs work any harder, got rid of 'safe' seats, or stopped negative campaigning. By contrast, our first-past-the-post voting system has been copied around the globe. It is used by 2.4 billion people, making it the most widely used system in the world. 3. AV is expensive AV would end up costing our country an estimated £250m. This referendum alone is costing us £91m and AV would be a more costly way of running elections. Australia's elections under AV cost three times more than ours do. When preferential voting systems were introduced in Scotland and London, expensive vote counting machines were bought in at a cost of millions. That's without even counting the need for more polling stations and election staff because av ballots take longer to complete. 4. AV hands more power to politicians AV is a politicians' fix and will do nothing to fix our broken politics. By boosting the number of Lib Dem MPs, AV makes hung parliaments more likely - leading to more broken promises, more back-room deals, and more power in the hands of politicians rather than the voters. If AV was the answer to the expenses scandal, why didn't we hear about it at the time and why are Members of the European Parliament abusing their expenses even though they're elected under a different system? 5. AV supporters are sceptical Even the Yes campaign think av isn't good enough for our country. Those people telling you it is the best thing since sliced bread have spent years pointing out its flaws. Nick Clegg dismissed it as "a miserable little compromise" while Chris Huhne said "there would continue to be safe seats where the MP will effectively have a job for life". But now they've all changed their tune. AV remains unfair, obscure and expensive and would be bad for our country. That's why people should vote No.