Darren Barrenger, Labour's Prospective Parliamentary Candidate for Harwich & North Essex

During recent weeks the scandal around MP's expenses has engulfed the media. Out of the storm has come a growing cry for electoral reform with MP's being given more power to hold government to account and be less restricted in their voting by their own party whips. But the most controversial and arguably the most important demand has been the one for a complete reform of the system of voting that is currently used to elect MPs to Westminster.

I have launched a poll on my website but wanted to back that up with some useful information about the different types of system, to help people with a genuine interest in our democracy with some background to help them enter the debate and make up their own minds.

Listed below are the main electoral systems that we could consider as part of any reform.

First Past the Post

The system currently used for electing members to the British House of Commons is a plurality system with single member constituencies. Winning candidates simply gain more votes than any other candidate on a single count. This need not be an absolute majority of the votes cast in a constituency.

The Alternative Vote (AV)

The Alternative Vote, which like FPTP is based upon single member constituencies, is a majoritarian system. Winning candidates secure the support of over half the voters in a constituency. The vote is exercised by recording preferences against the candidates on the ballot paper. If no candidate receives more than half of the votes cast on the first count of first preference votes, the candidate who received the fewest first preference votes is eliminated and his/her second preferences are distributed between the other candidates. This process continues until one candidate has achieved an overall majority.

Supplementary Vote (SV)

The Supplementary Vote is similar in method and purpose to the Alternative Vote, the key difference being that, under SV, voters are limited to indicating a first and second preference. Where candidates receive more than a half of first preference votes cast on the first count they are deemed elected. If not, all but the top two candidates are eliminated and their second preferences redistributed. The candidate with the greatest share of the resultant vote is elected - in the majority of cases, but not necessarily, this will be with more than half of the votes cast.

Second Ballot

As with the Alternative Vote the main objective of the Second Ballot system is to increase the chances of a candidate being elected on an absolute majority of the vote. Voting takes place on two separate days. If any one candidate fails to achieve an absolute majority after the first ballot a second ballot takes place. Where more than two candidates are allowed to progress to the second ballot a majority result cannot necessarily be guaranteed but, typically, candidates not performing well in the first ballot will withdraw and throw their support behind a candidate with a better chance of winning.

List Systems

The rationale of list systems is to translate directly a party’s share of the vote into an equivalent proportion of seats in parliament. The precise proportionality of such systems will, however, be influenced by such factors as whether the country is treated as a single constituency for the purpose of voting and the allocation of seats (some systems involve the use of smaller, regional or sub-regional units or two-tier districting), the use of differing electoral formulae for the allocation of seats and the use of thresholds.

Single Transferable Vote (STV)

The Single Transferable Vote system is essentially preferential voting (as in AV) in multi-member constituencies. Voters are to able to rank as many candidates, both within parties and across different parties, as they wish in order of preference. Any of those candidates who reach a certain quota are deemed to have been elected. The surplus votes of candidates elected on the first count and the votes of those with fewest votes after subsequent counts are distributed on the basis of preferences to the remaining candidates until sufficient candidates reach the quota and are, as a result, elected.

Mixed systems: the Additional Member System (including AV or SV Top-up) and Parallel Systems (AMS)

The title of mixed system describes any system which combines a list system element together with a plurality or majoritarian single constituency system. Under an additional member system, voters cast two distinct votes - the first for a constituency MP and the second a party vote. The allocation of additional members then serves to correct the disproportionality which arises from the election of single constituency MPs. Under a parallel system, the two votes are independent of each other and the additional members exist to mitigate rather than correct any disproportionality in the return of constituency members.