On February 4, the Labour Party's national executive committee endorsed the main proposals of the Collins Review to change the party's membership and decision-making structures. Tomorrow's special conference will do the same, with the result that:

n Affiliated trade unions will no longer cast any kind of collective vote in elections for party leader, deputy leader or London mayoral candidate. Instead, members of affiliated unions can opt to become cut-price "affiliated supporters" of the Labour Party and vote in these elections as individuals.

n Trade unionists who until now have paid a political levy and thereby been able to vote in deciding their union's position in Labour Party elections will be disenfranchised. They can only participate in future if they become affiliated supporters (but with no vote in local party organisations), "registered supporters" (ditto) or, much more expensively, full members of the party.

At the February 4 Labour NEC meeting, all union representatives except one from Unite voted for this dog's breakfast. A subsequent meeting of the Unite executive council decided - despite the severe misgivings of many present - to switch the union's position to support the reforms.

This helps ensure that the changes will receive near unanimous approval at tomorrow's special conference, with only some MPs, constituency activists and Young Labour representatives voting against.

Thus all the biggest union affliates - Unite, Unison, the GMB, Usdaw and the CWU - will help speed the beginning of the end of the Labour Party as the mass party of the organised working-class movement.

It has long been the party which seeks to reconcile working-class interests with those of British monopoly capitalism and imperialism.

But its trade union, class base has also held the potential to make Labour a party and a government that, alone in British conditions, could enact far-reaching reforms that benefit workers and their families.

We had such reforms from Labour governments in the mid-1940s and 1970s and in the late 1990s, although the social democratic trend in the Labour Party has always steered shy of shaking the foundations of capitalism itself.

Stifling the collective voice of affiliated trade unions within the party will severely limit that potential in future, raising serious questions for all who want radical reform in Britain - and especially for socialists and communists who want to see a fundamental transformation of society.

So why are trade union and party activists and some left Labour MPs helping to remove the remaining wheels from their party as a vehicle for substantial change?

First, they do not want to embarrass Labour Party leader Ed Miliband in the run-up to next year's general election. He has nailed his yellow colours to the mast over these reforms.

Last May, running scared from the right-wing media in league with new Labourites, Miliband had summoned the police to investigate whether Unite officials had tried to rig the selection of Labour's parliamentary candidate for the Falkirk by-election.

Shockingly, it seems, she had turned out to be a working-class trade unionist rather than a backroom policy wonk, a media consultant or a defecting millionaire Tory MP.

In July, Miliband's cowardly response to charges that Labour was still being manipulated by trade union "barons" was to propose "reforms" that would further weaken the collective influence of unions in Labour Party affairs.

These were later incorporated into the ongoing review of Labour membership and decision-making structures by Baron Collins of Highbury.

To keep up the pressure on Miliband, the Ineos management at Grangemouth oil refinery then suspended the senior Unite official at the centre of the Falkirk allegations and subsequently locked out the aggrieved workforce. The SNP joined the Tories in attacking Labour's inability to control its union affiliates.

Second, some reluctant "reformers" may have convinced themselves that the proposed changes really will open Labour up to a democratising and radicalising inflow of trade union supporters. They may even imagine that they can influence how the mass of their own members will vote.

All available evidence suggests otherwise.

Currently, unions affiliate to the Labour Party some 2.7 million of their members who pay the political levy.

Of these, only 235,000 - fewer than 10 per cent - voted to decide who should lead Labour after Gordon Brown in 2010. Many were already full party members. How many more will now opt to enrol as affiliated supporters is - even by the most optimistic estimates - unlikely to exceed the number who voted back then.

Certainly, the decision almost three years ago to allow registered supporters to join the party for free and eventually take part in leadership ballots has been a flop. Indeed, Labour Party officials refuse to disclose the figures.

So far from drawing more of the 2.7m levy payers into active affiliation with the Labour Party, the impact of the Collins proposals will be to exclude them altogether.

Moreover, affiliated unions will henceforth be excluded from the balloting process and so will no longer be able to issue a collective view to the rump of affiliated supporters, alongside the ballot papers.

The loss of several million affiliated members would deplete Labour Party coffers by up to £7m a year in affiliation fees -around a quarter of the party's budget - over a five-year transition period.

Some unions will doubtless attempt to plug the funding gap with hefty general donations, irrespective of their members' views and with little or no ability to influence party policy.

We can also expect a new drive for bigger state aid to the Westminster parties, in the teeth of widespread public opposition.

While a looming general election may attract more new members, registered supporters and individual affiliation dues, this will be limited should Labour fail to adopt and implement policies that appeal to people who have had enough of austerity and privatisation.

Third, some gullible trade union leaders have been mollified by the promise of a review of the new system around 2019.

They, of all people, should know that reviews are invariably promised by leaderships when they want a reluctant membership to swallow unpalatable schemes handed down from the top table.

These latest changes - due to be in place by the end of this year - will not only continue, of course. They will be extended into such areas as the trade union share of the vote at Labour's annual conference.

In fact, the whole thrust of organisational "reform" in the Labour Party from the 1990s and Partnership in Power onwards has been to reduce trade union influence locally and centrally, close down genuinely democratic and participative decision-making and concentrate ever more power in the hands of the party leadership.

Making Labour safe for big business has been the central purpose of this process, championed by the new Labourites.

Already, we have reached the point where Labour conference policies can be ignored, as with renationalisation of the railways, while party leaders proclaim others - such as the creation of foundation hospitals and the introduction of student top-up fees - for which they have no democratic mandate.

That tomorrow's special conference is scheduled to conduct its momentous business in just two hours speaks volumes about the leadership's contempt for inner-party democracy.

Finishing off the trade unions' collective and sometimes decisive role in the election of an omnipotent party leader is, therefore, an even more significant step than finishing off the annual conference as a forum for debate and policy-making.

Furthermore, another new "reform" raises the threshold of support needed in the Parliamentary Labour Party to stand for the party leadership from 12.5 to 15 per cent.

This makes it even more difficult for a socialist to run than left MP John McDonnell discovered in 2010.

For the Communist Party, however, tomorrow's decision does not invalidate the case for securing a Labour victory at the next general election.

This will still be necessary in order to get rid of the present unelected Con-Dem regime. Victory will raise people's morale and open up the opportunity to exert pressure on a Labour government through the trade unions and campaigning movements such as the People's Assembly.

Yet the need for a Labour victory may now be a tactical question rather than a strategic one, if the Labour Party no longer contains the potential to play a positive and major role in the struggle for socialism.

It will be akin to socialists in the US voting for the Democratic Party as the "lesser of two evils" rather than as a vehicle for socialist advance.

In the new political conditions being prepared by this year's Labour conferences and next year's general election, how should the Communist Party and other socialists respond?

Rob Griffiths is general secretary of the Communist Party of Britain. Read part two of this two-part series in tomorrow's edition