Like the Levellers, the Tolpuddle martyrs or the Jarrow marchers, the Chartists of the 1830s and 1840s are up there among the Labour party's most venerated secular saints. And rightly so. For the Chartists long ago placed democracy, reform and fairness at the front of the British labour movement's forward march.

In case a brief recap is necessary, the People's Charter consisted of six points: universal male suffrage, voting by secret ballot, annual parliaments, abolition of the property qualification for MPs, payment of MPs – and equal constituencies. The point of this last demand was to secure "the same amount of representation for the same number of electors – instead of allowing small constituencies to swamp the votes of larger ones". Classic fairness, in other words.

It tells you something about today's Labour party that it is no longer willing to go into the parliamentary lobbies in September to advance the equality of representation for which the Chartists campaigned. Instead it will enter the lobbies with the opposite goals. It aims to block a reform that would equalise parliamentary constituencies. And it seeks to protect an unequal status quo of over-empowered smaller seats of which Labour is the main beneficiary. It will do this, moreover, in the largely deluded belief that it is engaged in the noble work of preventing the kind of electoral gerrymander that was used to exclude catholics in Northern Ireland, or black and poor people in the United States, from the exercise of their rights.

The accusation of gerrymandering is one of the most serious any party can make. It is tantamount to an accusation of electoral corruption. It makes the probity of the electoral system – and thus of the laws made by those who hold power under it – a public issue. It is a step along a road which leads to the claim that those who govern under such a system have an illegitimate mandate, and so that those who are ruled need not be bound by their laws. To be sure, we have not reached that point yet. Even so, an accusation of gerrymandering is not something that should be made lightly.

Yet this is the accusation – "the worst kind of gerrymandering in the world" was the astonishing phrase that Jack Straw used on the radio today – which Labour is levelling against the coalition's plan to equalise the size of constituencies before the next general election. Moreover, it is the smokescreen behind which Labour, in its spasm of poisonous indignation against all things Cleggite, now also plans to vote against the bill which prepares the ground for a referendum on the AV system that Labour itself endorsed in its manifesto less than three months ago.

Some of Labour's objections to Nick Clegg's new bill have validity. It is true, for instance, that governments proposing change to the electoral system ought to consult opposition parties before finalising their plans, partly because such subjects deserve consensus but also to allay suspicions that the plans are partisan. Yet this bill has been published as a mix-and-match done deal between the coalition partners, even though this is only the very start of the parliament.

It is also true that the abolition of local inquiries into objections to new boundaries undermines confidence in the impartiality of the process. This is particularly the case with such a big process – even though such inquiries in the past have rarely changed anything, while countries like Australia and New Zealand manage perfectly well without inquiries at all. And the coalition's proposed exemption for up to four northern Scottish seats, three of which are held by the Liberal Democrats, is special pleading; if all constituencies are equal, none should be more equal than others.

The objection that a more comprehensive electoral register should be in place before the constituency equalisation process begins also has weight. Yet Labour's anxieties would ring truer if they had done more about the process during the last 13 years. One reason they did so little is that all parties suffer from low registration, not Labour alone. Inaccuracy of registers is also a fact of life, and the UK's estimated 92% accuracy is by no means the worst. Even though Labour's objections are mostly delaying tactics, not objections of principle, it clearly makes sense to take six months to reform the register first.

Yes, the reforms are being forced. But this does not add up to gerrymandering, let alone the worst kind in the world. A process whose statutory governing principle is equality of electorates, conducted by independent boundary commissioners, is at heart a just and proper process, not political skulduggery. Clegg has been too prescriptive and peremptory in some respects, but in the end his is still a legitimate objective, and a full parliament ought to provide sufficient time to see it through.

Be clear, therefore, that Labour is not trying to protect fairness from those who would destroy it but to perpetuate an unfairness from which Labour itself benefits. Inequality of constituencies is not the only source of bias in the electoral system – but it is certainly one of them. For the past five parliaments it has been biased towards Labour. No amount of red herrings about the danger of reducing the number of MPs, or the inappropriateness of including more than one major change in the same bill, should be permitted to distract from the essential propriety of correcting that bias. To claim this bill should be opposed because it is partisan is not just opportunism, it is an Orwellian inversion of the truth.

The principled stance would be to give the reform bill its second reading. Both of its main pillars – equalising seats and paving the way for the AV referendum – are progressive reforms. If Labour wants to make alliances with rightwing Tories to unpick the bill during the committee stage it can then try to do so, though it would not be right.

This week's decision to oppose the bill on second reading, however, defines Labour both as a party that is a defender of unequal constituencies and one whose commitment to AV reform has quickly become conditional. It raises the question of whether Labour will now, in fact, campaign for a yes vote on AV at all. When Labour looks at this bill it sees Clegg – whom it now hates – not electoral reform, which it should and until a few weeks ago did support. Nearly two centuries after the Chartists, one is bound to ask whether the Labour party is any longer a party of reform at all.