AN ALTERNATIVE WE COULD DO WITHOUT

The Guardian leads today with news that the government is set to propose the introduction of the alternative vote for elections to the House of Commons – which, if true, would be deeply depressing.

Under AV, single-member constituencies are retained from the current first-past-the-post system, but voters mark their ballot papers not with a single "x" but by numbering their preferences. If no candidate gets more than 50 per cent of first preferences, the bottom-placed candidate is eliminated and his or her second preferences are added to the other candidates' totals, and so on until one candidate tops 50 per cent.

In practice, its main effect would be to ensure that results in marginal seats were determined in most instances by the second preference votes of supporters of third- or fourth-placed candidates. In nearly all the Labour-Tory marginals that decide British general elections, that would mean Lib Dem supporters deciding whether they'd rather keep Labour or the Tories out.

On one hand, this would reinforce the already stifling trend in British politics towards lowest-common-denominator populist politics. And on the other, as Lib Dem supporters' second preferences piled on the agony for whichever of the major parties they disliked more, it would also exacerbate the in-built tendency of FPTP to yield landslide election results.

Although in 1997, 2001 and 2005 this would probably have benefited Labour, throughout the 1980s, when Liberal and Social Democratic Party voters generally saw the Tories as less bad than Labour, it would almost certainly have given Margaret Thatcher even more commanding majorities than she actually won.

Under the present electoral system, Labour is in danger of losing its overall majority at the next election on a very small swing to the Tories (as the document referred to in this story from the Sunday Times yesterday makes clear). Labour supporters of AV, believing that Lib Dem voters would be more likely to make Labour rather than the Tories their second choice in 2009 or 2010, think that AV would be a neat way of saving those imperilled seats. But if their assumption about Lib Dem voters is wrong – as it could be – a change to AV could easily deliver a Tory landslide.

The problem, put simply, is that, far from yielding a House of Commons that more accurately reflects the spread of party support across the country – which should surely be the goal of any change to the electoral system – AV could make the Commons less representative. It is not a step towards proportional representation but a step away from it - and as such deserves nothing but contempt from democrats across the political spectrum.