Delegates agreed by just 50.9 per cent to 49.1 per cent the resolution welcoming the reaffirmation of Clause IV by last year's conference.
While unions voted by 36.6 per cent to 33.3 per cent against the traditionalist resolution, constituency delegates voted for it by a margin of 17.4 per cent to 12.5 per cent.
As part of reforms introduced by the late John Smith at last year's Labour conference, the unions' share of the vote was cut from 90 per cent to 70 per cent, with constituencies taking most of the rest.
Under the old system, the platform would have won the day, albeit narrowly. The result served to underline traditionalists' argument that while the union block vote might be negative in terms of public relations, it has invariably served to moderate the instincts of constituencies.
The Transport and General Workers' Union, the party's largest affiliate with 14 per cent of the vote, backed the clause in the debate yesterday.
However, Bill Morris, the union's general secretary, is understood to believe the resolution will signal the start of, rather than an end to, discussions over a new constitution.
A meeting of delegates representing the Unison public service union decided to back the controversial resolution with little debate. According to left- wingers, Tom Sawyer, a senior offical with Unison, fought shy of a debate within the delegation because he expected to lose it. Among those lining up with the T & G and Unison were the construction workers of Ucatt, the RMT transport union, and Aslef, the train drivers' union.
The second-biggest affiliate, the GMB general union, backed the platform in rejecting it, arguing that it had opposed a similar motion at the TUC last month. Among the unions also supporting Mr Blair were: the Amalgamated Engineering and Electrical Union; Usdaw, the shopworkers' union; MSF, the white-collar union; and the Union of Communication Workers.Reuse content