If we’ve learned anything from politics over the past year, it’s that the era of two party politics seems to have crashed into a long-overdue end.

We are now faced with a crossroads: either we allow the UK to succumb to single party hegemony, or we pry open the door to pluralistic politics and allow a truly democratic multi-party politics to thrive.

Failure to achieve proportional representation could leave us facing unending Conservative governments for the foreseeable future – something we desperately cannot afford at this time of poverty and climate crisis.

However, this article isn’t written to make the case for proportional representation. That case has already been effectively made by many other writers. Instead, we need to move our discussion onwards from why we need proportional representation and onto how we can go about getting it.

The threat of continued environmentally reckless, right-wing rule in the UK has led to more and more talk about the possibility of forming some kind of ‘progressive alliance’, emerging to deliver real democracy and to pose an alternative.

Indeed, it has been encouraging to read advocates from across different progressive parties making the case for a progressive alliance. Encouraging words from prominent members have come from the SNP, Labour and the Green Party.

So, how do we get there?

There are clearly plenty of us who believe that ‘progressive’ parties need to start to discuss privately and publicly – to at least consider the possibility of – some kind of electoral pact, a ‘popular front’ that would look to avoid fragmenting the vote among ‘ourselves’ in winnable seats, and that would look therefore toward electing a Parliament in 2020 that would have a progressive majority for democratic change. For mending our broken democracy.

How do we move from general talk to action? Well, we need to have some kind of plan. The think tank that I chair, Green House, has gone beyond op-ed articles toying with the principle of progressive-pacting: we have produced a multi-authored report looking into how a ‘progressive pact’ could work, and thinking through a number of its pros and cons in some detail.

Our report will be formally launched this Friday at Green Party Conference in Birmingham, at a unique panel in the main Conference hall. It will be unique, because on the panel will be not just Caroline Lucas MP, myself, and Zoe Williams of The Guardian chairing, but also Neal Lawson of Compass and Labour, Lisa Nandy MP of Labour, and Chris Bowers of the LibDems. This is perhaps the possibility of progressive alliance already present, in outline.

In order for such a pact as our report envisages to actually fly, it would have to be done in such a way that has real advantages – real possibilities of gains – for all parties involved in it. Political pluralism in this country is not going away. It is ludicrous of Labour’s elite to think that they can win on their own in 2020. Greens are going to have to be an ingredient of such a victory – as are the ‘Nationalist’ Parties, and the Lib Dems too.

While the importance of Labour and Green cooperation is crucial to ensuring a progressive majority in 2020, it is unlikely to be enough on its own without significant input from other parties. Martin Robbin recently illustrated this point in the Guardian, where he noted that even with Greens supporting Labour candidates in large droves, we are likely only to see between 7-11 seat gains for Labour.

If we’re serious about ensuring a progressive majority and electoral reform, then we need to work with others as well as the Labour Party.

The Labour Leader says ‘No’?

It is going to be very hard to get a progressive pact to happen. Jeremy Corbyn, who one might have expected to have been sympathetic to the idea, has seemingly ruled it out – even for the specific case of Caroline Lucas, the Green Mp for Brighton, whop is much closer to Corbyn politically than the great majority of Labour MPs.

But to be fair to Corbyn, he is in the middle of a bruising leadership election. It would be challenging for the Leader of the Opposition, in the middle of such an election campaign, to come out in favour of acting with other parties. It would have required great vision and bravery.

Corbyn is highly likely to win the leadership election. Once he has done so, and with Labour almost certainly continuing to struggle internally and in the opinion polls, then my bet is that he will think again, and start to face reality: without a progressive alliance, Labour will be destroyed by the Conservatives. But with such an alliance, a better future is possible.

And there are historical precedents for this idea, which were no doubt similarly disparaged as pipe-dreams when they were first floated. The most striking such precedent is the 1903 pact with the Liberals that in effect enabled Labour to get into Parliament in the first place in numbers, in 1906.

There are powerful historical arguments for the consideration of such pacts by Greens. Let me briefly address directly those who do or would like to support my Party, the Party hosting this debate at its conference next week …

The only way that a new party managed to break through in a significant way, early in the 20th century, was through an electoral pact with an old party. Then it was Labour with Liberals. Now it could be Greens, with Labour and Liberals and nationalists. This progressive alliance idea is about enabling change, under the crazy First Past The Post system, and enabling growth for the Green Party. (Of course, as soon we get electoral reform, everything will open up.)

1903-6 saw an electoral pact in some seats that enabled a good new small party to grow exponentially (and that prevented what would otherwise have been a disastrous long Tory hegemony under FPTP). Just what some of us in the Greens are proposing now, and asking colleagues in other parties to hear and to join in with.

Such a pact now could have even more exciting and long-lasting results than it did back then, if it brings electoral reform in its wake! And support from all parties – and that includes Labour – for proportional representation must be a sine qua non of any progressive pact.

A more recent precedent is the little-known ‘non-aggression pact’ between Labour and Lib Dems which in 1997 was responsible for the scale of the destruction of the Conservatives at the hands of both those parties, and in particular of the largely-successful ‘decapitation strategy’ that they jointly practiced, that year. Here is a rare mention of that pact, which was unofficial and involved Labour and Lib Dems not doing work in each others’ target seats.

Real leadership for a new progressive politics

You might think that a progressive pact is an attempt at a fix, bypassing the voters right to democratically express their will. Not so. This is about enabling more people to vote for what they believe in and to get it:

• By achieving PR, which will at last end tactical voting which was still an utter bane in 2015. Many millions of voters did not vote for what they believed in, because of FPTP. (In Cambridge, where I stood as MP-candidate, we reckon there were at least c.5-6k Greens who voted Labour, for example.)

• By seeking to ‘trade’ (vote-swap, if you will) Green votes in some marginals, votes that would otherwise mostly be tactically squeezed into semi-non-existence anyway, for enabling Green votes en masse in seats where, under the pact, we will be able to win. (And the same goes for Labour, and for the LibDems, and for Plaid Cymru…)

In sum: in 2020, a progressive pact would enable people to vote for (and achieve!) what they believe in. It would give voters the option of an alternative to endless Tory rule, an end to FPTP, and an end to our broken system. A chance for citizens to really take back control …

If it is going to happen, it will take a lot of doing. So we have to get started now! The obstacles, as I’ve already admitted, are of course manifold, from inertia to tribalism. But put simply: it’s time to take the bold step, together, of seriously considering such a pact. The prize is democracy itself, not to mention getting rid of the Tories.

With both the Green Party and Labour coming to the end of leadership contests this September, it is crucial that a ‘progressive alliance’ is one of the things that new leaders prioritise. As members or supporters of political parties, we must use this opportunity to force the issue onto the agenda. For a ‘progressive alliance’ is now the only feasible alternative to continued Conservative government in 2020.

Any leader or leadership contender in any ‘progressive’ party who fails to recognise this risks ‘leading’ their party – and, more important still, their country – only into the dustbin of history.

Rupert Read was Green Party candidate for Cambridge at the 2015 General Election, and is Chair of Green House. He writes regularly for the Ecologist.

The report: Green House think tank’s new report on the progressive pact concept.

Thanks to Atus Mariqueo-Russell for research for this piece.