Recently, just about everyone has an opinion about how Labour can fix its middling poll ratings and win the upcoming election outright. Combine all the advice and you get a nice simple message: it needs to be simultaneously more left and rightwing, while ensuring it remains centrist. Easy.

But I have an even easier proposition, and something that – and I don't say this lightly – is virtually guaranteed to give Labour a landslide win in 2015. What's more, it'll draw in voters from the Lib Dems, Ukip, SNP, Plaid Cymru and Greens alike. It'll even pull in a handful of Tories, and not just those who slipped and put their X in the wrong box. But it does have one tiny drawback.

OK. Here's the manifesto. Don't worry, it won't take long to read. In fact, it's 485 pages shorter than Ukip's 486-page long 2010 opus, with room for overbearing stock photography, generous spacing, and a size 72 font:

Within 90 days of forming a government, we will vote on changing the Westminster electoral voting system to Proportional Representation, and then call a snap election.

That's it.

“PR? That's your big idea?” I hear you cry.

Yes, but think about it: a single-issue party with a chance of getting voted in, and then the guarantee of an instant second election? Ukip, the Greens, the Liberal Democrats, the SNP, Plaid Cymru, Respect... all of them would have to stand down and put their weight behind this once-in-a-lifetime chance to get rid of the hated First Past the Post, the system that limits their chances of making real progress.

Anyone can put electoral reform in their manifesto, tucked away somewhere at the back where only the most bored politico would spot it (Labour has done it in two of the last four elections), but to make it your entire manifesto: people would know you're serious. I can see the campaign now: "Vote Labour now, so you don't have to in 90 days", with a grinning Ed Miliband holding the pledge card.

The Conservatives would panic, and the press would go bananas, but if you get everyone bar Tory voters behind the Labour party, then current polling would suggest a turnout of around 67 per cent to Labour and 33 per cent to the Conservatives. Ironically, First Past the Post's archaic mechanisms would deliver a healthy, decisive majority at this point, just as David Cameron promised it would when he campaigned against AV.

Indeed, my entirely unscientific attempt at replicating this on May2015.com's result calculator gives Labour 567 seats to the Tories' 58. A handful of seats are held by "others", mostly in Northern Ireland. Presumably the DUP managed to get onto the extremely sparse leaders' debates in this fantasy world.

This would lead to the unusual spectacle of the still fresh government voting to bring itself down, what with the Fixed Term Parliament Act meaning the Prime Minister can't unilaterally call an election. The Tories wouldn't know how to vote.

The chances of this happening? Close to zero. The Labour party is extremely well aware of how well First Past the Post serves the party, and how PR would be giving this away forever. The chance to govern based on 35 per cent of the vote would slip away, with only the delicious prospect of the Tories doing even worse to soothe Labour heads. There's a fair case to be made that that's what’s slowly happening anyway, but that's for another piece.

So, if you're reading, Ed: here's an incredible chance to go down in history as a genuinely reforming, albeit short-lived, Prime Minister with a share of the vote Blair could only dream of. You could even put nationalising the railways in size 6 font at the bottom of that one page manifesto, and try to slip that in too, if you fancy.

Alan Martin (@alan_p_martin) is a freelance politics, science and technology writer