Election Special 4: First past the post now - but what will future UK elections look like?

In the last of our public law team's Election Specials we look beyond today's General Election to consider what's on the table in terms of electoral reform.

At the 2005 General Election the Labour Party formed a government with 356 seats in the House of Commons and a share of 35 per cent of the votes cast. The Conservative Party won 198 seats with 32 per cent of votes cast. The Liberal Democrats came third with 62 seats on 22 per cent of the vote. The result was a telling demonstration of the inability of the first past the post system to allocate seats in proportion to the percentage of votes cast.

The 2005 Parliament has been dissolved. Now, as we await the shape of the 2010 Parliament, it appears that reform of the electoral system is a priority for voters, and that this campaign has lifted electoral reform to the top of the agenda.

And yet before the starting gun on this campaign was fired, the UK Government had proposed a referendum on a form of proportional representation. This proposal - contained in an amendment to the Constitutional Reform and Governance Act 2010 - did not survive the final "wash up" days of the old Parliament. In this referendum that never was, by October 2011 the electorate would have been asked whether or not they preferred an "alternative-vote system" to the current first past the post arrangements.

Labour's alternative-vote system

Under the alternative-vote system proposed by Labour, each constituency would continue to elect one MP. However, rather than vote for a single candidate, voters rank the candidates in order of preference, with 1 as first choice, 2 as second choice etc. After all ballots have been cast, the first choice votes for each candidate are counted. Where one candidate has more than 50% of the votes cast that person is duly elected.

Where no single candidate has enough votes on the first count, the count begins again. But on this second count, the candidate with the fewest number of votes from the first count drops out of the race. The votes originally cast for the last placed candidate are then re-allocated to the next choice candidate of each voter, with the last placed candidate dropping out. After the second count, if there is still no candidate with 50% of the new vote, the re-allocation process begins again with the new last placed candidate dropping out and their votes being re-allocated. This process continues until a single candidate crosses the 50% finishing line.

Liberal Democrats...