Dear Liberal Democrats,

As your party gathers in Brighton, the end game of your amazing governing odyssey, and whatever life takes place after it, can no longer be avoided. And the question is this, given it's impossible to imagine you are going to govern alone, who would you rather form a coalition with in less than two and half years' time: the Conservatives, Labour or simply the biggest party?

The electorate will help you make the actual decision, of course. If the numbers say it has to be the Tories again, then you must decide how to deal with that – coalition or confidence and supply? But I ask again - not what you think might happen but what do you want to happen and, therefore, what will you do to make it happen?

As someone who has long argued and worked for a progressive alliance in British politics, I can understand the maths and electoral reality. Being the third party means hoping no one has overall control and therefore a share of power for you. I can also understand how difficult it is to be a junior partner in a coalition. You have helped show that coalitions can work. People may not like the policies, just like any single party government, but they cannot say it's been weak. But it's not strong government, whether single party or coalition, that we ultimately want, but governments with the right sense of purpose and direction.

You can’t be blamed for the electoral outcome, but what you can't be forgiven for is not trying to achieve the best possible result.  If you genuinely don’t care which party you deal with, or if you would rather stick with the devil you know - then fine. But if you would rather see a progressive centre-left coalition then A) good and B) how are you going to help create the conditions in which you get one?

Now, I know your first reaction will be "but what about bloody Labour". What indeed? I’ve written endlessly about the party's problems and will continue to do so, but for all of Labour's faults, most of its hearts beat to the same rhythm as yours. It is on the side of poor and the dispossessed.

Of course, my party, which I'll turn to next week, has to grow up and decide whether it wants to stay in the wilderness or govern in partnership in the event of a hung parliament.  It’s a huge test. In a recent survey, 57 per cent of Labour List readers said they didn't want to talk to the Lib Dems. Unison general secretary Dave Prentis has said he will halt a pact. If Labour doesn’t secure a majority, one can only presume that they would rather have another centre-right coalition. So it won't be easy. Labour has a cultural revolution to go through to be part of the modern world.

It's likely that the test is coming. The pollster John Curtice has long predicted a hung parliament at the next election. He recently wrote, "the hung parliament brought about by the 2010 election was no accident. It was a consequence of long-term changes in pattern of party support that mean it is now persistently more difficult for either Labour or the Conservatives to win an overall majority". Bookmakers, too, think the next parliament will be hung.

In 2010, the centre–left collectively failed the people of this country. It must never do so again. It was a dereliction of duty that no one had done the policy work or built the relationships required for a progressive coalition. The numbers made it tough, but we weren’t even ready before the polls closed. Shall we leave it to Michael Gove and David Laws to stitch it up again?

That’s why we have to build relationships now – through policy, ideas debates and campaigns. We might find we have more in common than we think. Everything good about liberalism is social – it was New Liberalism that founded the welfare state and Beveridge who gave it its post-war form. It was Keynes who helped rebuild the post war economy and it is a Keynes we need today. On Europe, constitutional reform, climate change, civil liberties, a Plan B or Plan C, the best of both parties would provide a half-decent programme for government. Labour needs to be more liberal. The Liberals needs to be more social. So can we start to sketch out the outlines of a new coalition agreement to rebuild Britain? This doesn’t mean either party losing its identity or distinctiveness, it does mean preparing for the best feasible outcome.

So tell Vince Cable to keep texting Ed Miliband and Labour’s leader to keep texting back. Ed Balls should continue to find ways to agree with St. Vince and vice versa. Peter Hain should keep stating the obvious: that Labour should prepare for coalition with the Lib Dems because it will struggle to win an overall majority at the next election.

As the Tories shift right and Labour tries to refashion itself under Miliband, who do you really want to work with next time? Charles Kennedy, Shirley Williams, Tim Farron, Ming Campbell, Paddy Ashdown, Simon Hughes – what do you want given you won't win alone? And if you want it, what are you prepared to do about it?  

The political crime would not be to react as best you can to the verdict of the people – it would be to have failed to even try and build something different and better before the people speak and in, so doing, influence what they might say.  For that, we all have a responsibility.

Enjoy your seaside break – and I look forward to your answers on a postcard.

Neal

Neal Lawson's column appears weekly on The Staggers.