Supporters of the principle assert that the public's perception of Labour and therefore its electability is at stake.
The debate will centre on what power unions should wield over the Labour Party in future. Should the influence simply reside with members?
A special review group over the links encountered such sensitivity on the issue that it abandoned any attempt to make recommendations. The committee, which included senior politicians and union officials, had been working towards a formula in which union members maintained influence over the election of Labour leaders and the selection of MPs.
The group, however, was leaned on heavily by senior party figures and Labour's national executive this month will simply be presented with a list of options. Thus the argument will provide a succulent bone of contention for union conference delegates.
One element of the argument has been resolved. Apart from some parliamentary purists, most now agree that the union block vote at policy-making conferences should be reduced rather than abolished and that it should be made to look more democratic.
It is seen to provide an important moderating counter-balance to constituencies, some of which have proved themselves vulnerable to 'entryists' from the far left.
The best guess now is that the union vote, having dropped from 90 per cent to 70 per cent, will decline further to about 50 per cent. The speed with which it drops will provide the only room for disagreement.
Under the favoured system, the union vote at conferences is likely to be deployed by individual delegates and not by general secretaries holding up cards with their union's block vote written on them. The difference is largely cosmetic because on important issues union delegates will be bound by union policy. Nevertheless, this issue seems to be moving toward resolution.
In the areas of leadership elections and selection of MPs, however, it is 'all to play for'.
The review group was meant to remove the conflict from the public arena, but now it is difficult to see how a bout of highly public blood-letting can be avoided.
In April the battle will begin in earnest when the Amalgamated Engineering and Electrical Union, the third biggest party affiliate, will reaffirm its conviction that only members of the party should be allowed a vote.
The conference of the GMB general union, the second largest party sponsor, however, will be intent on preserving input from trade unionists. The GMB has suggested that payers of the political levy in unions should be able to register as party 'supporters' locally and qualify for a vote.
This will be followed by the deliberations of the Transport and General, the biggest affiliate, which will also be keen to retain a union influence. There seems to be little consensus, however, between those who oppose one member, one vote on how the union input should work.
The MSF manufacturing union could tip the balance. It is understood that the union is moving towards support of one member, one vote. Given the enlarged 30 per cent voting share of the constituencies at the conference, the MSF decision could be critical. The constituencies are expected to vote overwhelmingly for one member, one vote.
The debate is by no means academic. Unions have warned that they will be less disposed to fund the party they created if they have limited influence over its key decisions. Labour has been landed with a pounds 2m overdraft at a time when it is seeking to build a pounds 10m fighting fund for the next general election.
But in the words of Tom Sawyer, a senior figure in the party and deputy general secretary of the National Union of Public Employees: 'No say, no pay'.