There is a very astute article in the New Statesman by Green party leader, Caroline Lucas, attacking the Labour party for its ingrained tribalism and calling on the leadership candidates to demonstrate their pluralist credentials.

If there was a Monopoly Commission in British politics, then it would almost certainly be having a word with Labour over its support for a wildly unfair voting system that artificially inflates its support in Parliament whilst denying smaller parties representation. But given the absence of such an organisation, it seems we'll just have to make do with Lucas's efforts.

Caroline Lucas speaking in Parliament. 

The country's first Green MP is asking the leadership candidates to support her amendment to the Parliamentary Voting System and Constituencies Bill so as to offer a PR option on the ballot paper in the forthcoming referendum.

As Lucas puts it:

I am tabling an amendment that would rewrite the referendum question to allow people to choose from a wider range of voting systems, including properly proportional options such as the additional member system (used in elections for the Scottish Parliament, Welsh Assembly and Greater London Assembly) and the single transferable vote (used in Northern Ireland). As the Labour leadership battle narrows in favour of the Miliband brothers, I challenge them, even at this late stage, to support my amendment, to demonstrate their commitment to both pluralism and democracy.

Both Ed and David Miliband have gone out of their way to portray themselves as pluralists who understand the need for Labour to connect with other progressive forces. They have both extolled groups such as London Citizens, claiming they want Labour to be a broad-based "movement" and not a top-down party machine.

Yet at the same time they have given every indication that they wish to preserve an antiquated constitutional system that offers the very opposite of pluralist politics. As Caroline Lucas says, in common with much of their party, at times the Milibands seem to long for the good old days of diarchy and the tribal certainties it offered. 

Until Labour moves beyond tribalism, beyond wishing the "extinction" of other political traditions, it remains destined to repeat the mistakes of the past. At recent Compass conferences, I have discussed the need for a more progressive, pluralist politics, based not on Blair's suffocating "big tent", but on a campsite of different parties and movements, sharing common values but maintaining their own identities.

Seeing Lucas speak at one of these Compass events last year, at the Labour party conference, provided me with a vivid lesson in the tribal tendencies within the party. There was an atmosphere of tension accompanied by jeering and heckling led by the Labour activists from Brighton. One woman next to me looked as though she was ready to explode, as though she'd just heard a diatribe from Nick Griffin rather than a reasoned speech from a fellow progressive. I breathed a sigh of relief when Lucas made it out in one piece!

If the Milibands are true pluralists then they are going to have to tackle this culture within their party, which has been around for at least as long as their father's Parliamentary Socialism: a Study in the Politics of Labour which provided an analysis in 1961 of the party's attachment to the central institutions of the British state, not least first past the post.

At the moment, both Milibands are hostile to PR and luke-warm in their support for AV, the mildest form of electoral reform we could have (witness David's remark that we will "cross that bridge" when we come to it). This conservatism does serious damage to their claims to be a force for progressive renewal.

But it's not too late. If they were to declare themselves supporters of fair votes and back the Lucas amendment it would pull the rug from under the Lib Dems. It wouldn't be an excuse to oppose AV, of course, if the amendment effort fails, but it would show they are serious about being a force for democratic modernisation. The question is, do they have the nerve?

Read more about the AV referendum in OurKingdom's Referendum Plus section.