Voting has begun to elect the next general secretary of the Unite union, a decision that could define the direction of the Labour party for years to come.

Allegations of personal smears, political interference and cronyism have characterised a fraught campaign to lead Britain’s biggest union, which isLabour’s most generous donor.

With Labour 19 points behind the Tories, the Unite result could decide if the party fragments or remains in its current form.

The incumbent, Len McCluskey, is the favourite having gained 1,185 branch nominations – five times more than his nearest challenger, Gerard Coyne, a senior Unite official from the West Midlands.

McCluskey is backed by those on the party’s left, such as Jeremy Corbyn and John McDonnell, who believe that his victory will ensure the left has some influence over Labour’s machinery and will be able to push through rule changes that could give them greater control.

Coyne is backed almost universally by Corbyn’s enemies, who believe an unexpected victory would rob Labour’s leader of his last significant union backer and paymaster.

Coyne’s team believes there is still hope, if they can persuade a higher turnout of Unite’s 1.4 million members to vote. The low turnout in internal elections – 15.2% voted in the 2013 general secretary contest – hands disproportionate influence to its radical activists, many of whom see McCluskey as too rightwing.

Coyne’s strategy is to focus on motivating members who do not usually turn out. If he can persuade 20% of members to vote, anything could happen.

Coyne’s team believes members are angry at the way McCluskey and his allies have spent hundreds of thousands of pounds of union funds on what are perceived as McCluskey’s pet projects, such as Corbyn’s leadership.

The front page of Coyne’s campaign website highlights a Guardian story that showed that last year the union contributed more than £400,000 towards the purchase of a £700,000 central London flat for McCluskey. Unite has argued that such deals are commonplace among large unions.

Coyne, 49, is also asking members if it is right that McCluskey, 66, has sought another five years when he is above retirement age and drawing his pension. The union’s policy on retirement is that “68 is too late”.

Gerard Coyne is backed almost universally by Corbyn’s enemies. Photograph: Steven Murphy

Corbyn’s stance on defence, fracking and pharmaceuticals might also bring supporters on board, Coyne hopes.

But they face an uphill struggle. McCluskey is backed by influential forces on the left – both the Daily Mirror and the Morning Star have been accused of giving the incumbent an easy ride – and has an efficient internal machine of loyal activists.

Criticisms from Coyne have angered McCluskey’s supporters, for whom loyalty to the union means not bringing its name into disrepute.

McCluskey, a former employee in Liverpool’s dockyards, has the advantage of a national profile, as well as being a formidable operator at branch level.

His campaign has won the largest number of nominations ever, including from defence workers at the Faslane and Coulport naval bases in Scotland and the Barrow shipyards in Cumbria – despite Corbyn’s opposition to Trident renewal.

Some Labour MPs are concerned that McCluskey has a unique position of influence over the party. Unite gave £175,000 to finance Corbyn’s 2015 campaign to become leader, his friends and former Unite employees, such as Karie Murphy, are in some of Corbyn’s key positions and his union’s votes at party conference and on Labour’s national executive committee can force through rule changes.

If McCluskey is re-elected, some Labour MPs believe there will be a move to change the rules for reselection for MPs – potentially threatening their jobs and a Labour general election victory if the party swings too far to the left.

There could also be a rule change to reduce the leadership nomination threshold from 15% to 5% of the parliamentary party. As most MPs are to the right of the Labour membership and union leaders, a reduction in the parliamentary party’s influence would make it more likely for a leftwing candidate to get

McCluskey appeared on Andrew Marr on Sunday saying that Corbyn needs to show he can win round public opinion within the next 15 months to retain the party’s support.

In a statement released on Monday, Coyne compared McCluskey to a 1970s “union baron”, throwing his weight around in Westminster, making and breaking political careers.



“That kind of behaviour is for yesterday’s men. With vast changes coming to our economy, a union leader should be focused day in, day out, on issues like Brexit, zero-hours contracts and the shifting nature of work,” he said.

Corbyn’s allies and Labour MPs led by the party’s deputy leader, Tom Watson, last week focused their attention on the contest, following claims uncovered by a secret recording that Unite will give funds to Momentum if McCluskey is re-elected.

Watson said McCluskey appeared to be part of an entryist plot; McCluskey, backed by several members of the shadow cabinet, said there was no deal with Momentum and accused Watson of being a conspiracy theorist.