The Staggers 24 June 2015 Trade unions accused of withholding members' details in bid to sway Labour contest Unions said to be restricting affiliated supporters' data to preferred candidates. Unite general secretary Len McCluskey speaks at the Labour conference in Manchester in 2014. Photograph: Getty Images. Sign UpGet the New Statesman's Morning Call email. Sign-up One of the main grievances aired during the last Labour leadership contest was that the candidates did not have equal access to affiliated trade unionists. Ed Miliband, who was endorsed by the big three unions (Unite, the GMB and Unison), was given an automatic advantage over his brother - one that ultimately secured him the prize. Labour's new electoral sysytem, which Miliband introduced in 2014, was designed to end this unfairness by requiring members of affiliated unions to formally register as supporters. The party would finally have access to their contact details and could provide them on an equal basis to all candidates. Figures released yesterday by Labour showed that 3,778 affiliated supporters have so far signed up to vote in the contest, compared to 9,115 registered supporters and 246,469 members. Sources suggest a simple explanation for the relatively low union figure: the unions are holding back details of many of those who have registered. The motive, they suggest, is to ensure that only preferred candidates in the leadership, deputy leadership and London mayoral contests have access to their members. Some predict that as many as 100,000 will have been affiliated by 12 August, the deadline to participate (a claim recently probed by Stephen). The unions are required to transfer all data by 31 July to allow Labour to cross-reference details (ensuring no individual has more than one vote). But the numbers involved are perhaps less important than the principle. If the chosen candidates are perceived to lack legitimacy owing to the unions (as Miliband was), the Tories and others will not be slow to exploit this fact. Update: A Unite spokesman said: "There is absolutely no truth in this story whatsoever. We are complying fully with party rules and procedures, and we would have told the New Statesman this if they had bothered to ask. It is a further gratuitous smear of trade union engagement in the Labour Party." › Leader: The retreat of social democracy George Eaton is senior online editor of the New Statesman. Subscribe For daily analysis & more political coverage from Westminster and beyond subscribe for just £1 per month!