The battle for 29 April has started

New Labour versus Old Labour: In the latest in our series on the strugg le within Labour, Barrie Clement analyses the unions' part

It is highly unlikely Tony Blair will ever capture the hearts and minds of trade union activists. He will, however, need their votes.

The clash over Clause IV inside the labour movement illustrates the cultural chasm between the social democratic Blair and the socialists, radicals and traditional "Labourites" who form most of the union movement's movers and shakers.

The political convictions of union activists range from farleft feminists to crusty old right-wingers, some of whom have more in common with Musso- lini than Marx. Genuine social democrats are thin on the ground.

A leading light in the leftist "Defend Clause IV" ginger group asserted the party had moved so far to the right it had left the moderates wallowing in its wake. Even supporters of Catholic Action, a secretive force for political moderation in the union movement, are unenthusiastic about Blair's proposals for a "New Labour Party", the source said.

Politics apart, active trade unionists simply do not like the cut of the leader's jib. He is an arriviste. He has failed to serve his apprenticeship in countless stultifying branch meetings.

Clearly, grass-roots union members are a different kettle of fish. On most issues they are probably only slightly more left-wing than the electorate. While the "average" union member is unlikely to be a "Blairista", as they are now called, he or she probably has more in common with the Labour leader than those who attempt to serve their industrial interests.

That impression was reinforced when members of the Transport and General Workers' Union, the party's largest affiliate, voted for Mr Blair in the ballot for the Labour leadership. Bill Morris, T&G general secretary, together with the union's senior activists, had let it be known that traditionalist John Prescott was the union's man. It was a salutary lesson for those who believed there might just be an umbilical cord between leaders and led in the union movement.

Average union members, however, are not being asked their opinions on Clause IV. Mr Blair will have to convince the activists. Despite reforms, the unions will test opinion on the future of the constitution through branch consultation. Only those for whom trade unionism is a hobby habitually turn up to branch meetings.

Unions, which will command 70 per cent of the vote at the special conference on the clause on 29 April, are also consulting their rule books and referring to their previous conference decisions before deciding their position.

Despite the introduction of a free vote among trade unionists at policy-making conferences, delegates will face a "three-line whip" on 29 April. In all its essentials, the block vote lives.

In the likely absence of support from the constituencies, Blair needs the unions. He is relying on the persuasive MrPrescott, the deputy leader, to engage in the disagreeable business of delivering the critical union vote. Union activists are much taken by the irony.

At a private meeting this week with officials of public service union Unison, Mr Prescott allowed it to be inferred he was unenthusiastic about his leader's challenge to Clause IV. But he appealed to the pragmatic side of their political nature.

Even the relatively moderate GMB general union is by no means "in the bag", according to left-wingers.

One senior GMB activist believes John Edmonds, the union's general secretary, may have considerable difficulty in delivering the union to Blair. "His big problem as far as the GMB is concerned is the water industry. People want a commitment to renationalisation and Blair won't give it."

As 29 April approaches, the pressure to indulge in vulgar horse-trading will become more intense. Confidential assurances from the leadership about its intentions may not be enough.

Blair and Prescott will need to invest the new Clause IV with union-friendly phraseology such as "common ownership" if they are to win support. Most unions will reserve their final pronouncements until the new wording is published.

The prime ministerial Blair will doubtless introduce a Bill providing for state funding of political parties, thus ending unions' hold over Labour. But the short-term trick will be to take the unions with him.

Clause IV will not be the end of the matter. There are several other issues which will engender conflict between the two wings of the movement. Unions want the Labour leadership to attach a figure to a future national minimum wage. Mr Blair would prefer to "see the Treasury books" before committing himself. And unions are seeking detailed employee rights which the Labour leader believes might scare the business community. Most sensitive is the issue of trade union power. Activists want as much Tory legislation as possible repealed. Mr Blair would prefer to keep it to a minimum.

Unions want some political muscle in return for funding Labour. Mr Blair is anxious not to frighten the electoral horses.

On Clause IV, perhaps a storming last-minute speech by Mr Prescott will do the trick. Whatever happens, Mr Blair will have been forcibly introduced to the practical politics of the movement. And it will have given him a taste of the constraints on his vision of "New Labour".

Tomorrow: Nicholas Timmins on Blair's drive for mass membership