Advocates of electoral reform - most of whom are otherwise "New Labour" Blairites - privately admit defeat is likely, unless Mr Blair steps in to defend the policy.
Their bitter disappointment will add to internal unease over the pace of Mr Blair's self-styled "revolution", after Saturday's plea from Roy Hattersley, of the traditional right wing, for a restatement of the party's commitment to fight poverty.
A senior Labour Party source accepted there would be a row over the referendum. "It will be dropped, and there will be a bang when it is dropped."
But leadership sources said yesterday: "We are committed to a referendum on proportional representation. That remains the position. There are no plans whatever to change it."
Only three motions calling for the referendum to be ditched have been submitted, but opponents are organising a wave of amendments to be sent in which would guarantee a vote.
The critical decision will not be taken until the national executive meeting on the Sunday at the start of the conference, when Mr Blair is expected to ask the executive to adopt a neutral position on the issue, allowing the conference to decide.
Last month, Mr Blair told MPs opposed to the referendum that if they wanted to scrap the policy, they had to ensure they could win the vote in Brighton.
Derek Fatchett, a Labour defence spokesman and organiser of a group defending the present first-past-the-post voting system, said yesterday that, as a result of shifts in a number of key unions, "I would be very confident that we would win".
The public services union Unison switched sides at its Scarborough political forum in May. Sources said the GMB general union was "flexible" - technically the union supports a referendum but is against changing the voting system. Even the AEEU engineering union's position is in doubt. Its electricians' section agreed a motion for the Scottish Labour conference saying the party's consultation on the issue had not shown "any desire by the electorate for proportional representation".
Mr Fatchett said that if the policy were to be dropped, it would be better to do it in October. "The other possibility is simply to exclude it from the manifesto."
Mary Southcott, of the Labour Campaign for Electoral Reform, said yesterday: "It would fuel the cynicism about politics and politicians if Labour tried to stop a debate about what many believe is a corrupt voting system, just because Labour appears about to benefit from it."
She claimed the conference vote would depend on the union block votes - just as it was agreed to cut their share of voting power from 70 to 50 per cent for the 1996 conference. And she warned that Mr Blair's reputation for trustworthiness - already trailing Mr Smith's, according to this month's Gallup poll - would suffer. She drew attention to Mr Blair's statement during the Labour leadership election last year that he supported a referendum on electoral reform.
The main argument influencing Mr Blair is understood to be that a referendum would split the party. It is argued that the Liberal Democrat leader, Paddy Ashdown, could not insist on a referendum as the price of co-operation after the next election, because there is no electoral support for change. But Mr Smith, who also opposed change, was persuaded of the case for a referendum so that the people, rather than politicians, could decide.Reuse content