There's been some confusion about the Trade Union section vote in Labour's leadership contest quite apart from mendacious attempts by Tories, Blairites and sundry ignoramuses to turn it against Ed Miliband. And that confusion is about the low turn out. I believe that while the turn out was abysmally low and is a cause for concern, it isn't particularly surprising.
Political science makes a distinction between first and second order elections. Here in Britain the one election widely perceived "to matter" is the general election, simply because it determines who runs the government for x number of years. Other elections to council, devolved parliaments/assemblies, the European parliament, and referenda are second order because they are not perceived to matter so much. Hence their turn out is much depressed (which is why it's generally a good thing to run second order elections on the day of the general, if at all possible).
A similar process is at work in our trade unions. Firstly most union members do not join because they want to participate in its decision-making structures. Finding a member who's been to a regular branch meeting is a rarity. They join because of the protections unions offer at work. As a consequence the votes that tend to matter for most members are those relating to industrial action of some kind. This is the unions' 'first order' election.
The second order elections, from the standpoint of everyday workers' relationships to their union do not matter. In this category falls general secretary, officers', executive committee and, of course, Labour leadership elections. So quite how the Socialist Party comes to the absurd conclusion that the low turn out and high spoiled ballot paper rate is "because none of the candidates reflected their urge for radical socialist policies to meet the challenge of the current devastating economic crisis" is beyond me, especially when Roger Bannister, standing in this year's Unison general secretary's election, could only persuade 2.76% of the entire membership to vote for his "radical socialist policies".
The low turn outs for all second order elections reflect the weakness of the labour movement as a whole. Now is not the time to moan about how members should "take an interest". Instead the labour movement has to make more effort to listen and speak to their concerns.