The Labour leader will hail the result as a turning point in the party's history, and he will declare that it clears the way for Labour to "win power because of our principles, not despite them".
The Independent has learned that senior Labour Party figures, including members of the Shadow Cabinet, are targeting the trade union power base on the ruling National Executive Committee for radical change.
Some leading modernisers are seeking to strip the NEC of its policy-making powers and limit its role to a management committee in charge of party discipline.
Mr Blair's supporters were still engaged last night in a campaign to win over last-minute union conversions to proposals that will end the party's commitment to wholesale nationalisation and explicitly acknowledge the contribution of the market to a healthy economy.
About 56 per cent of the vote at the conference was virtually " in the bag" for Mr Blair. Within that figure, 35 per cent would come from unions and 21 per cent from constituencies.
The decision of the party's largest affiliate, the Transport and General Workers Union, was known to be in the balance; the 75-strong T&G delegation will command more than 14 per cent of the vote.
The voting at today's delegation meeting of the MSF white-collar union, the sixth largest affiliate wielding 3.8 per cent of the conference votes, is thought to be on a knife edge, while the public service union Unison, with 11.5 per cent of votes, seems to be the least likely to change. The union's political fund committee yesterday recommended that its 24-strong delegation abide by a decision to oppose the Blair reforms.
Mr Blair has secured the support of enough unions to win, but the leadership is delighted to have won 8-1 support from the party's constituencies, which carry 30 per cent of the vote compared to the unions' 70 per cent.
Of the constituencies which balloted, about 419 out of 422 had voted for change by last night and around 70 more were yet to be declared.
Mr Blair will tell the conference the Clause IV debate, criticised by the left, has helped to win new support and attracted thousands of new members.
Moves are expected to cut the trade union block vote at party conferences from 70 per cent to 50 per cent, reflecting the growth in membership power.
The first step to changes in the NEC could be to reduce the hold trade unions have over it by reducing the 12 trade union seats on the 32-strong executive.
A Shadow Cabinet source said: "What we have to do is end this double- headed hydra of the NEC and the Shadow Cabinet. There has been perennial tension between them. We have to put in places arrangements to sustain a Labour government rather than undermine it as it has done in the past."
Jack Straw, a leading Shadow Cabinet moderniser, said: "Tony has achieved a revolution in the party and it will never be the same again." Writing in the Independent today, he says that Neil Kinnock supported his campaign for change.
John Prescott, Labour's deputy leader, last night confirmed that the party would give British workers the first legal right to keep their jobs when they go on strike.
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