In a recent comment article I wrote about my hopes and fears about the new coalition. To put it another way, to what extent did I regret my decision, which I explained in a pamphlet I launched with Nick Clegg and a shorter accompanying piece in the Guardian back in March, to endorse the Liberal Democrats?

As a self-professed left-liberal, surely I must have been feeling sore when my newly-adopted party jumped into bed with the Conservatives? No, I wrote, I felt neither betrayed nor chastened. Awkward sometimes, nervous pretty much every day, complacent, never. It has not been an easy decision, particularly when the odd blogger embarks on a customary “Judas is a term too good for you” green ink rant.

But when Tom Watson asked me to pen a few thoughts on what might entice me back into the Labour fold, the offer was too sensible to resist.

I don’t see the issue of allegiance as a simple trade-off. One of my strongest criticisms of Labour, whether “new” or “old”, was its tribalism. I have not swapped one tribe for another. My appeal is for a broader based pluralist politics, embracing the best from all parties, and none. Some of the strongest politics is taking place far away from the musty building in SW1 where MPs reside, and in which the public has so little faith. Much of it revolves creating a more liberal Britain.

But back to Tom’s question. I’ll break it down into three main areas: policy, vision and behaviour.

Policy: Labour achieved some notable successes, from the minimum wage to civil partnerships, but its actions were determined essentially by cowardice and fear. Whether Iraq (Blair’s ingratiation with Bush) or the banks (bail-out plus supine non-regulation), Labour was fearful of the Right. It played to the lowest common denominator. It was authoritarian on criminal justice and weak on political reform. Contrast its criminal-justice agenda with the last three months which have seen ID cards abandoned, stop and search abandoned, child asylum-seeker detention abandoned.

Vision: In all the 13 years of the Labour government, I could not fathom what the vision was. What was the abiding principle? I concluded, with reluctance, that the most important priority was to win, and to keep the other lot out. A tribe is a group based around social affinity and common interests; it is not a vehicle for change or inspiration.

Behaviour: It was this ideological emptiness that led the Labour machine to behave in the way it did. By ‘machine’, I mean the inner core around Blair and Brown. I exclude a number of ex-ministers and MPs who acted with greater self-knowledge, people like Robin Cook, Mo Mowlam (both sadly long departed) and Jon Cruddas. Peter Mandelson’s book provides the definitive word on the narcissism and bullying that we all wrote about – and were denounced for writing.

So where does Labour go from here? The leadership contest has been unedifying. This is due to its length, to its narrow audience, but also to a more fundamental lack of ideas. In the absence of Cruddas, I hope that Ed Miliband wins. But the victor will achieve little if he does not ensure that Labour searches its soul.

The party needs to ask why, at the height of public anger over the banks, it was the Left and not the Right that received a kicking across Europe? The critique needs to go beyond media ownership (valid though that point is) and incorporate imaginative and self-critical thinking about the role of the state and individual in a world that long ago moved on from Bevan and bed pans.

The coalition faces a rocky road ahead. Many people will suffer as the cuts bite. I will be as critical as the next person. I don’t see politics as a zero-sum game; you’re with us or against us. Britain needs a credible Labour opposition and when the times comes a Labour government of some sort again. It won’t happen until its politicians show greater personal humility and greater political courage.

John Kampfner