On this morning’s edition of the Today programme, the Shadow Education Secretary, Michael Gove, was challenged on the Conservatives’ opposition to electoral reform. Gove reiterated the familiar arguments advanced by senior Conservatives throughout the campaign about the supposed advantages of first-past-the-post (FPTP) elections.

The Tories’ argument is essentially twofold. First, the constituency system makes it easy for the local electorate to throw out their MP, if s/he turns out to be corrupt or to be poor at their job. Second, FPTP produces decisive overall election outcomes, particularly when there is popular desire among the national electorate for change, giving the party of government a clear mandate to implement the manifesto which it put to the voters.

There is a superficial logic to this point of view, which some voters find intuitively appealing. However, the arguments simply do not hold water when set against the evidence.

The problem with the first part of the argument, focussing on local voter power, is that the UK’s electoral geography is so remarkably static. In the great majority of seats, it is highly unusual for local electorates to ‘get rid’ of a sitting MP.

Almost two-thirds of Labour and Conservative MPs elected in 2005 were returned with majorities of at least 15 per cent. Such seats rarely change hands, however loud the local grumblings about how the sitting MP does his or her job. Before the votes were cast at the 2005 General Election, 407 constituencies in Great Britain (two-thirds of the total) were deemed to be either ‘ultra’ or ‘very’ safe. Just 10 of these 407 seats (2.5 per cent) changed hands as a result of votes cast in 2005.

A few years ago it was fashionable in some political circles to argue that large majorities (and low turnouts) were simply a reflection of ‘voter contentment’ and relative satisfaction with the role played by local MPs.  But that was before the expenses crisis. I assume there is no longer any real need to explain the flaws in this particular defence of the phenomenon of ‘the safe seat’.

The second part of the argument is just as shaky. At the 2005 General Election, 39 per cent of registered electors did not vote at all (to which we should really add the 10 per cent or more who were eligible, but not registered).  Among those who did vote, 35 per cent voted Labour. Labour’s 60 seat majority in 2005 was therefore delivered on the basis of a mandate comprising the support of 21.6 per cent of registered UK electors (under 20 per cent if we add unregistered voters).

While Labour’s vote in 2005 constituted the lowest level of popular support for a government in the post-war period, the notion of a clear ‘electoral mandate’ has been questionable for decades. No party has won more than 45 per cent of the voters cast in a General Election since Edward Heath’s Conservatives in 1970. The last Prime Minister to take office on the basis of his/her party having gained the support of more than one-third of the electorate was Macmillan in 1959. The chances of David Cameron coming anywhere near to the levels of support gained by his predecessors are zero.

To be fair, there are some voters who possess the sort of power, locally and nationally, which Gove claims is inherent to FPTP. In 2007, following the ‘General Election that never was’, the Electoral Reform Society estimated that the difference between a Labour and a Conservative victory could have depended on how as few as 8,000 voters across 30-35 key marginals cast their votes.

This tiny minority of the electorate fortunate enough to live in the most marginal seats have powers which the rest of us do not possess. In 2005, almost half of the seats deemed ‘ultra marginal’ changed hands. The magnetic draw of these seats to the party leaders has predictably been evident throughout the 2010 election campaign. As a Democratic Audit briefing released yesterday argues, some voters are more equal than others.

That just leaves one small matter to clear up. When challenged to explain why most academic political scientists tend to favour some form of proportional representation, Gove’s response was essentially ‘show me an academic in favour of PR, and I will show you a member of the Labour Party or the Liberal Democrats’. It was a slightly desperate response, but just in case anyone needs to know - I am a member of neither.

Democratic Audit’s General Election Briefing, A tale of two electorates - why some voters are more equal than others, can be downloaded here.