I agree with Nick. The Alternative Vote is, to borrow a much-quoted line from the leader of the Liberal Democrats, a "miserable little compromise". The pledge to hold a referendum on AV was a wheeze from Gordon Brown in the dying days of New Labour; there was no mention of it in the Tory or Lib Dem manifestos. AV isn't proportional, won't get rid of safe seats and might exaggerate Commons majorities.

Nonetheless, I'll be voting in favour of AV, and not the existing first-past-the-post (FPTP) system, in the referendum on 5 May. AV might have its flaws but FPTP isn't fit for purpose. It is a broken relic of the two-party era that gives disproportionate power and influence to a tiny band of swing voters in a handful of marginal seats in Middle England. Under AV, MPs are forced to command at least 50 per cent of the vote in their constituency - in 2010, under FPTP, two-thirds of MPs were elected without the support of a majority of voters in their seat.

First-past-the-post has failed on its own terms. In a recent speech, David Cameron claimed that the ability to "kick out governments" was the "best thing" about our present electoral system. Perhaps the Prime Minister has been living in a different country from me. In my 32-year lifetime, and over eight general elections, the government has changed hands just three times - in 1979, 1997 and 2010. Of the three election-winning prime ministers during this period - Margaret Thatcher (1979, 1983, 1987), John Major (1992) and Tony Blair (1997, 2001, 2005) - not a single one secured a majority of the votes cast.

Easy as one, two, three

Unable to defend or justify FPTP, the opponents of AV have resorted to deceit and dishonesty. Myths abound. The Alternative Vote isn't a foreign system. From trade unions to workplace committees, professional societies to student groups, millions of Britons already have experience of voting under AV. It doesn't require expensive voting machines, or cost £250m. To quote the comedian and Yes2AV campaigner Eddie Izzard: "The cost of AV is pencils." AV isn't a "confusing system" (David Cameron) or "fiendishly complicated" (Daily Mail). If the Australians can manage to rank candidates in a 1-2-3 order, so can we. AV doesn't automatically result in hung parliaments: over the past 100 years, Australia has had fewer hung parliaments under AV than the UK has had under FPTP. Meanwhile, Canada, despite using FPTP, has been beset by hung parliaments in recent years.

AV doesn't violate a "fundamental British principle - the principle of one person, one vote" (Sayeeda Warsi). Redistributing second, third or fourth preferences isn't the equivalent of casting a second, third or fourth vote. In the clever formulation of the Lib Dem MP Jo Swinson, speaking on BBC1's Question Time: "If I ask you to go and buy me a chocolate bar and say, 'I'd like a Mars but if they don't have that I'd like a Twix' and you come back with a Twix, I still only have one chocolate bar."

Opponents of AV claim that this last argument - centred around "one person, one vote" - is one of principle. But consider the results of last year's Labour leadership election conducted under - yes, you guessed it - the Alternative Vote. According to a recent study posted on the Left Foot Forward website, of the 102 Labour MPs who have signed up to the NotoAV campaign, 20 of them marked two preferences, seven marked three preferences, 12 marked four preferences and 41 MPs marked all five preferences.

These Labour MPs are not alone in their hypocrisy. Take the Tories. Under first-past-the-post, David Davis and not David Cameron might now be leader of the Conservative Party. In the first round of the party's leadership election, in October 2005, Davis got 62 votes to Cameron's 56. It was only in subsequent ballots, after the third- and fourth-placed candidates (Liam Fox and Kenneth Clarke) were knocked out, and the bulk of their supporters transferred over to Cameron, that he came out ahead of his rival in time for the postal ballot of Tory members.

What conclusion shall we draw? That there is one rule for the Conservative and Labour parties and another for parliament and the general public? Having won his own leadership contest with the help of second preferences, Cameron wants to deny the rest of us the same choice. Why wouldn't he? First-past-the-post delivered majority Tory governments on a minority of the vote for much of the 20th century.

So, is it any wonder that, in the words of the Lib Dem peer Matthew Oakeshott, the No campaign is "just a Tory front organisation"? The chairman, head of press, finance director, co-treasurer and key donors are all active Conservatives. It is difficult to avoid the conclusion that the L abour patrons of NotoAV - such as the former home secretaries John Reid and David Blunkett - are useful idiots.

Red/blue alliance

Enraged and obsessed with the Lib Dem "betrayal" last May, Labour tribalists have allied with the Conservatives (as well as the Murdoch media empire and the BNP) to defend the dysfunctional status quo. "Let's give Clegg a bloody nose," sneer Labour opponents of AV.

The embattled Lib Dem leader is a distraction. "Why hit the monkey when you can hit the organ grinder?" says the former shadow chancellor Alan Johnson. Cameron has as much to lose from the AV vote as Clegg - if not more so. The "pause" to the coalition's NHS reform bill is a reminder of how shaky the Prime Minister's grip on government is.

Meanwhile, backbench revolts are at a postwar high. As of February, according to Philip Cowley of Nottingham University, 76 Conservative MPs (representing a quarter of the parliamentary party) had voted against the government. Sixty of the 110 rebellions have involved only Tory MPs.
Cameron does not lead a happy party. The Prime Minister is neither loved nor feared by his colleagues in the way Thatcher was. A No vote in the AV referendum would give the PM a much-needed winner's badge and help him steady the Tory ship. A Yes vote would leave him branded a loser by his own unhappy party. Unlike the Labour Party, Conservatives tend not to tolerate losers for too long.

But the first and foremost reason to vote Yes on 5 May is to reform, improve and democratise our fractured electoral system - to vote for a fairer way of electing our MPs.

Correction: An earlier version of this article wrongly claimed that the MP Tom Harris had marked all five of his preferences in the Labour leadership election of 2010. He did not. He marked just one preference - for David Miliband.